An Obol for Charon (episode)
A mysterious sphere threatens the USS Discovery even as May, in her original form, implements a plan that puts Tilly's life in danger. Saru and Burnham's bond grows when Saru is forced to acknowledge a deeply unsettling Kelpien truth. Pike receives new intel on Spock from a loyal friend.

Summary

Teaser 
In the 's transporter room, Captain Christopher Pike greets Una Chin-Riley, his first officer from the still-disabled . Una reports that the ship suffered a cascading systems failure, and Chief Engineer Louvier had teams working around the clock. According to Una, the Enterprise is the only ship in Starfleet that has had any problems; Pike attributes it to the holographic comms systems, which Louvier had warned him against, and orders them removed in favor of "good old-fashioned viewscreens". As they reach the mess hall, Pike and Una discuss the allegations against Spock, which Una has used the time Enterprise has been in Spacedock to look into. Much like Pike himself, Una has difficulty believing the idea that Spock was capable of murder, and adds that the Enterprise crew is unaware of the details, only that he is in trouble. She adds that Starfleet Command has placed a Level One classification on Spock's case, an unusual move for a line officer, which led Una to do some digging; when asked if it was sanctioned, she admits that it was probably best Pike didn't know the details. Before looking at her information, Pike asks why she would bypass Federation protocols. Una believes something is not adding up about the investigation, and does not intend to let Spock go without a fight. Pike replies that as usual, they agree, just as he is called to the ready room for a briefing.

In the engineering lab, the  removed from Sylvia Tilly sits inside a quarantine chamber. Paul Stamets remarks that it should be given a name other than "May", and that while it looked like a formless blob, it was one of the most sophisticated lifeforms Stamets had ever encountered – it was sentient, and it had intentions. The mycelial network did not just connect life, but contained it, like an incubator. Tilly wonders aloud why it appeared to her as May Ahearn, leading her to think about the real May she had met when she was 14. She admits she had been a "weird kid" with few friends, and that no one including herself believed in her, but May did. Tilly thinks that she had not been the kind of friend that May needed, not even knowing that she was dead.

In the ready room, Michael Burnham reports she has cross-referenced the "Red Angel" with all known winged and avian lifeforms in the Federation, with no matches. Linus (after an initial universal translator difficulty) adds that it may not match anything in the known universe, to which Keyla Detmer speculates it may not be a species at all, but a unique individual. Whatever it was, Gen Rhys believes figuring out its connection to the signals would help identify it. Commander Nhan, on loan from the Enterprise, wonders what the "angel" needs. When asked for his opinion, Saru – clearly looking ill – apologizes, as he was awoken early fighting an acute rhinovirus – a cold, in other words. At that moment, Pike enters and orders the crew to stations, telling Detmer to set a course, 108 mark four, maximum warp. Noting that Saru was clearly feeling unwell, Pike orders him to rest, before having a word with Burnham. Una had given him the warp trail of the shuttle Spock stole from Starbase 5 while on her way back to Spacedock, and Pike has ordered the ship on an intercept course. Thinking back on her recent meeting with Amanda Grayson, Burnham believes she should not be involved in making contact with Spock, as she feels what she did to him would make things worse, not better. Pike disagrees, believing that facing what happened to Spock would not be easy, and that reaching him must be the priority.

At that moment, Discovery is violently pulled out of warp. Returning to the bridge, Pike orders red alert and shields raised. Joann Owosekun reports that she cannot raise the shields; Burnham's initial scans indicate a multiphasic stasis field, which interferes with the shield harmonics. Detmer's helm is unresponsive, and the ship has been brought to a complete stop. "Like a damn fly in a web," Pike says, just as Burnham points out the "spider" – a .

Act One 
Based on their scans, Burnham indicates that the sphere is 565 kilometers in diameter, with a mass of 6.39 kilograms, and melds organic and non-living matter. Linus adds that the sphere is also ancient, at least a hundred thousand years old. It has not responded to any hails, but is vibrating, and the computer has extrapolated what it might sound like based on the ambient radiation. Whatever it is, it has Discovery locked in place, and Pike orders Burnham to find a way to communicate with it or disable it. Burnham acknowledges his order in Klingon. Pike asks – in French – why she is speaking Klingon.

Returning to the bridge, Pike enters a scene of utter pandemonium, with the crew apparently speaking a variety of different Earth languages, including Norwegian, German, and Italian, as well as non-Human languages such as Andorian. R.A. Bryce explains, in Welsh, that the sphere answered their hails, resulting in the cacophony. The computer displays appear to be suffering the same problem. Burnham calls Saru to the bridge; as he enters, Pike welcomes him (in Hebrew) to the "Tower of Babel", and Burnham (in Mandarin Chinese) remarks that Saru knows more languages than anyone in the ship. Saru replies in the same tongue that he is fluent in 94 languages. Burnham then explains (now in Spanish) that the ship's universal translator has been infected with a computer virus, translating everything into different languages. Working through the various language barriers, Saru brings up the backup bridge translator, which will allow everyone there who speaks English to be understood. However, Detmer reports her console is another matter, believing the language she is reading is Tau Cetian. Burnham believes she can purge the virus from the translator's main interface; though clearly unwell, Saru offers his help, remarking that Burnham would need a translator just to operate the turbolift.

In the engineering lab, Tilly reports their section is unaffected by the virus, and that she will report if anything changes. Pike tells Stamets that if they can't get away on conventional drives, they will need to use the spore drive. Stamets acknowledges, and orders Tilly to bring the drive online. Just then, Commander Jett Reno, who had been rescued from the crashed , enters the room humming to herself, reporting that the universal translator for that section was "no más". She mentions that the chief engineer wanted her to firewall off the critical propulsion systems, but didn't think a "greenhouse" counted as either "critical" or "propulsive", "but what do I know? I'm just a gearhead, not a farmer." As she works, Reno debates with Stamets on the reliability of the standard antimatter and dilithium propulsion compared to the spore drive, mocking Stamets for thinking he can run a ship on "mushrooms that I pick off my pizza". Stamets retorts with the comparative cleanliness and renewability of the spore drive compared to conventional warp drive, the ecological ruin of dilithium mining and the battles fought to corner its supply, and how pollution nearly destroyed Earth two centuries earlier before everything was converted to solar panels. Reno remarks she could fix things with duct tape, if he preferred. Tilly then speaks up, asking if "May" had something to do with the sphere; Stamets sarcastically retorts that a giant creature from their universe and a being from the mycelial network had about as much in common as himself and the "grease monkey" Reno, to which Reno adds she could fix that analogy with duct tape as well.

At the computer mainframe, Burnham and Saru (now conversing in Russian) have isolated the communications system, and manage to restore the universal translation system on all decks. Just as Burnham reports their success to the bridge, Saru collapses to the deck, clearly ill with more than simply a cold. At that moment, the deck heaves violently; Burnham calls the bridge, asking if the sphere fired on them; Owosekun reports it did not, but the virus is spreading and causing the EPS conduits to overload. While Saru wants to return to the bridge to find out what was happening, Burnham instead takes him to sickbay.

In engineering, the power surges, releasing bolts of energy through the local relays. The computer seals the engineering compartment to contain the damage, but while life support is operational, Reno warns that the energy could ignite the oxygen in the air and "cook them like French fries". Tilly suggests diverting the power to act as a lightning arrestor; Reno adds that the door could act as a ground, and disperse the energy through the frame of the ship, but getting it from the relays to the door was the trouble. Stamets suggests linking the spore canisters, which contain a argon-xenon mixture he uses to prevent spore decay, as a makeshift lightning rod. Reno holds the transfer conduit up to the door and tells Tilly to hit the switch; the power surge knocks them off their feet and briefly disables the lights. As they flicker back on, Stamets checks on Tilly, whose hair is frizzled from the surge; she remarks that she felt like it was the second time she'd been hit by lightning that week. They then check on Reno, who remarks she'd had a strange dream about playing drums for . As he helps Reno to her feet, Stamets realizes "May" has escaped the quarantine chamber. "May" then attaches itself to Tilly's right arm, and will not let go.

Act Two 
Burnham, helping Saru through the corridors to sickbay, runs into Pike on the way; with communications disabled, Pike was on his way there anyway, and helps Burnham bring Saru in, hoping that Dr. Tracy Pollard can identify what is wrong with him. Dr. Pollard's scans show Saru has elevated heart rate, spiking adrenal levels, and increased neural activity, remarking that the amount of pain Saru was in would render most humanoids unconscious. Saru's threat ganglia then extend, and he reports he keeps seeing flashes of ultraviolet light, which Kelpiens can see while Humans cannot. Dr. Pollard asks if this is common among Kelpiens, at which point Saru becomes impatient, as the ship is in danger. Finally, however, he admits the condition is unique to his people, and that it is terminal. He believes the sphere has triggered vahar'ai, a biological process which signals when Kelpiens are ready to be culled by the Ba'ul, the predator species on his homeworld of Kaminar. While there are no Ba'ul present, Saru remarks that Kelpien ganglia are only so inflamed when they are near their end, and that those who undergo vahar'ai are either killed by the Ba'ul or succumb to madness. Either way, Saru says grimly, death is inevitable.

Tilly, with "May" attached to her, is placed within the quarantine chamber; Stamets tries to contact the bridge, but finds communications are down. Reno indicates that most of the ship's systems are disabled as well. Tilly begins drifting in and out of consciousness, remarking in a daze that she should be scared, but isn't, and that "May" means no harm. Stamets asks if she is able to see "May" again, and how she could know that "May" was benign; Tilly can only answer that while "May" was "clingy" and "wouldn't shut up", she thought that "May" needed her help, referring to the "plan" that "May" had needed her help with. From his scans, Stamets realizes that "May" is releasing a psilocybin hallucinogen into Tilly, which is influencing her emotional state, perhaps to keep her calm; Reno wonders if it's actually to keep her from fighting back.

Back in sickbay, Burnham speculates that if Saru believes the sphere triggered his vahar'ai, escaping from it could stop the process. Pike reminds her this would mean regaining control first; the computers are unreliable, and without computer control, primary systems could start failing, including the warp core. Life support is also slowly failing. If the sphere had intended to destroy them, Burnham wonders, then why the slow attack? Saru suggests creating "digital antibodies" as a means of slowing the virus' progression, but that it would take time. He volunteers to go along with Burnham to the science lab, remarking that while he is dying, he is not dead yet. Working together to create the antibodies, they are able to slow the virus' progression, with life support stable at 47 percent.

When Burnham tells him that he does not have to go through his ordeal alone, Saru admits that he has difficulty explaining to someone like Burnham how he comes from a race that submits, and how hiding is in his nature; he has learned so many languages, but has never shared his own, for fear of exposing his "alienness". He then asks for a favor: he has kept detailed personal logs since joining Starfleet, and asks Burnham to help catalog them so that the Prime Directive would no longer apply to his people, so they could know that they could have the same kind of journey as he had. Burnham, moved by the request, agrees. When asked if he recorded anything before Starfleet, Saru replies that his life began when he was granted refugee status by the Federation. While being processed at Starbase 7, he saw different lifeforms from across the universe, with far less than he had, but with a dream of something better. He listened to their stories, which awakened an empathic sense within him, and led him to join Starfleet so he could help others just like he was helped; Burnham calls him "the most empathic soul" she knows. The one caveat to that, however, was that he could not go home again. Before he can explain why, he is disoriented by more flashes of ultraviolet light, growing in strength and frequency. He tells Burnham that he can continue the work in the lab, and sends her back to the bridge.

Owosekun reports that Spock's shuttle is reaching the edge of Discoverys sensor range, and that even with sensors at maximum, they would not be able to keep a lock on him for long. The digital antibodies are doing their work, but the progress is sluggish; Burnham suggests that even if they can't contact engineering, someone should still go down there to check in, and asks permission to go down herself. Pike grants it, and Burnham hurries down to engineering, finding it sealed off. She learns from Stamets that he, Reno, and Tilly are trapped inside the lab and can't even reach the warp core, and that "May" has reattached itself to Tilly, taking her in and out of consciousness. When Reno remarks that they couldn't ask "May" what it wanted, Stamets suggests that perhaps they could, using the harmonic resonator he used to interface with the mycelial network, which would let "May" speak through Tilly. Burnham suddenly realizes that this was what the sphere was trying to do as well: using the virus to get into Discoverys computer as a means to communicate. Saru is able to see a pattern in the ultraviolet lights he has been seeing, like letters in a sentence. He realizes it was no coincidence that he began to feel the symptoms of vahar'ai just before they engaged the sphere, because it was not a creature making first contact; it was making last contact. It had reached out to Discovery because it was dying.

Act Three 
In the engineering lab, Stamets sets up the harmonic resonator, but the signal is weak, unable to reach "May". Reno suggests amplifying it with a cortical implant through trepanation – essentially, drilling a hole into Tilly's skull. Stamets sarcastically asks if she plans on fixing that with duct tape as well, before Tilly speaks up. She thinks Reno is right, and she thinks Stamets thinks that as well. "Then we do this together," Stamets replies. The only thing Reno could find was a power drill, hoping for a laser scalpel somewhere in the room; Stamets replies they will have to do it "old-school", and points Reno to the first aid kit to sterilize the drill bit.

On the bridge, Detmer is able to get the shields up, but they were still locked in place by the stasis field. Owosekun reports power fluctuations; Nhan adds there were still two dozen crew trapped below decks, with life support failing. From Tactical, Rhys detects an energy buildup inside the sphere, spiking 10,000 kelvin and rising. Pike asks if it was powering up weapons; Rhys detects no identifiable weapon signatures, but the internal temperature was now 20,000 kelvin. Pike orders all non-essential power to weapons, targeting the sphere's radial axis with photon torpedoes. Just then, Saru and Burnham enter and ask Pike to hold fire; the sphere was attempting to communicate with them, not destroy them. Saru explains that Kelpiens have empathy hardwired into their genetic structure, and that he could feel the sphere reaching out, trying to tell them something before it died. Burnham backs him up, saying she trusted his feelings implicitly. With Spock's shuttle six minutes from leaving sensor range, Pike tells them to keep talking, fast. Saru displays the ultraviolet light patterns he has been seeing on the viewscreen, and patches them through the universal translator, showing a multitude of languages. The sphere, he explains, was trying to use Discoverys computer to communicate with them, but it had overloaded them with information. If they lowered shields and allowed it full access, it could interface fully with the ship's systems. Pike is suspicious that lowering shields could be what it needs to destroy them, but Saru is insistent: the sphere does not wish to harm them.

In engineering, Reno manages to craft an amplified cortical implant using a communicator. Trying to prepare Tilly for the procedure, Stamets asks her to sing her favorite song, and they sing "Space Oddity" together as he drills the hole into her head, while Reno then places the implant. Tilly begins speaking with the voice of "May", which identifies itself as belonging to a species called the jahSepp, which was threatened by an "alien intruder" that began appearing at random intervals and damaging their ecosystem. Stamets asks if they were trying to reach out for help to stop a destructive presence, to which "May" replies that Stamets was the destructive presence, through his use of the spore drive. "May" broke through the network trying to reach Stamets, but instead attached itself to Tilly, taking the form of May Ahearn in order to elicit Tilly's sympathy, and allow "May" to deliver a message for Stamets. Stamets tells "May" that he can fix the problem if it would let Tilly go, but "May" refuses, saying it had "other plans" for her. When Reno attempts to detach "May" with a plasma torch, the parasite spreads, enveloping Tilly's body entirely.

On the bridge, Burnham reports the sphere's internal temperature is 1 kelvin and rising – the same temperature as a sun, indicating possible core collapse. Saru pleads with Pike to allow them to play their part in its destiny, to ensure that it will be remembered. Pike ultimately defers to Saru and Burnham's judgment, but orders Detmer to prepare to overload the warp core and eject it to destroy the sphere if things go wrong, and to prepare to ride the resulting shock wave. Saru instructs Detmer to lower the shields, has Bryce open all communications channels, and orders Owosekun to divert all computer power to communications. The library computers begin accepting the data, operating at twenty percent above maximum; whatever the sphere was sending, Burnham reports, they were getting it all. The transmission completes with seconds before the sphere detonates, but Detmer still has no control over the helm or even the warp core ejection; Pike orders full impulse, hard astern, just as the sphere explodes. Saru remarks that the light of its death throes was like music, to which Pike agrees... then wonders how they were alive to see it. Burnham reports that a nanosecond before detonation, the sphere reversed the polarity of its stasis field to push Discovery clear. Its final act was to save them, so that its story could be told. In engineering, Stamets uses the plasma torch to cut open the parasite (which releases a puff of spores in his and Reno's faces) and pulls Tilly out, then reports to Burnham that Tilly was alright. With the sphere gone, Saru tells Burnham that it was now his turn, and asks her to take him to his quarters. The entire bridge crew rises, watching, as Burnham helps Saru into the turbolift.

Act Four 
In his quarters, Saru shows Burnham a flower from his homeworld, which grew to mark the passing of the seasons on Kaminar; he had taken a few seeds with him when he left. He admits he had forgotten who he was when he left, focused on being "the best Kelpien in Starfleet", defined by his rank and uniform until that was all he became. Burnham says he is wrong – he found himself among the stars, his strength, his bravery. He had saved many lives, including her own. Saru then says it is time; he points Burnham to a Kelpien knife he kept in a drawer, a keepsake to prune his flowers, and asks her to use it to sever his ganglia so he could die in peace, before the pain and madness overtook him. He thanks her, calling her by her first name for the first time. Breaking down in tears, Burnham asks if it was truly inevitable. Saru is apologetic, knowing how many people Burnham has lost already, and that he would do it himself but he was too weak. After all they had been through together, Burnham admits that Saru was like family to her. Saru feels the same, that Burnham had taken the place of his sister Siranna on Kaminar, and that the blade had been hers, and that he had left her without saying goodbye. He asks Burnham to promise him, no matter how painful or frightening it was, that she would mend her relations with Spock, that if she could create that kind of bond with Saru, she could repair her bond with Spock. Burnham promises she will, and then raises the blade to sever his ganglia. But before she can do so, they wither and fall out on their own. Saru is confused, thinking he should be dead... and both he and Burnham break down in relieved laughter.

In sickbay, Dr. Pollard tells Saru that his vital signs are returning to normal, and asks how he feels. Saru confesses that he had never felt this way before, that fear has always been the guiding principle of his life, but now it was gone; more than that, he felt power, "my own power". Dr. Pollard thus certifies him fit for duty. Despite speaking 94 languages, Saru remarks to Burnham that sometimes words were not enough. Burnham tells him that the science teams reported that the sphere gave them more than just languages – it gave them its memories, everything it had ever experienced in a hundred thousand years. Its legacy would live on, and Saru's legacy had a new chapter. Saru adds it is a deeply troubling chapter; the Kelpien way of life had always been oriented toward death, and the role the Ba'ul played in it, which they knew as the "Great Balance". It had been their central, organizing truth... and Saru had proved it wrong, by becoming more than just prey to be culled. To Burnham's earlier question of why he could not go home, Saru explains that he promised Philippa Georgiou, when she had taken him with her years before, that he would uphold the Prime Directive and not interfere in the destiny of his people. But if what they had accepted as the truth was in fact a lie, he wonders, what would it mean for the Kelpien people and their world?

Burnham finds Pike in his ready room, reviewing some of the historical files from the sphere, specifically involving the war between the quaternary star systems and the Roquarri Imperium. Pike compares the sphere's information to the Dead Sea Scrolls, and remarks that Federation scientists would be studying it for centuries, yet wonders about the cost. Burnham replies that it had cost them nothing; the last thing the sphere had seen before its death was Spock's shuttle, and Burnham had been able to track down its trajectory. Pike calls the bridge and informs Detmer that Burnham would be giving her coordinates, ordering her to plot a course and "don't spare the horses". Pike tells Burnham that he would make sure she was kept at a distance from Spock, but Burnham, inspired by her previous conversation with Saru, says that no matter her mistakes, she wants Spock to know she would be there for him.

Back in the science lab, Stamets remarks it was time to close the door to the mycelial network, and begins making final calculations. Just then, Tilly begins hearing May's voice again, seeing her there for a moment, and then she was gone. Stamets and Reno tell her she was still coming down off the hallucinogen, but Tilly insists something is not right. Stamets and Reno, increasingly dazed, remark on one another's "aura", and note dust on their faces. Stamets realizes that "May" dosed them with psilocybin, and tells Reno to slap him hard across the face to focus him enough to get to the medkit, giving himself and Reno a dose of impedrezene. As their minds clear, they both realize Tilly is gone. Horrified, Stamets realizes that "May" has consumed her again.

Memorable quotes 
"I don't think the Enterprise will ever have a chief engineer more in love with his ship."
 - Pike, on Chief Engineer Louvier

"You know, he warned me. That damned holographic comms system.  Tell Louvier to rip out the entire system, from now on, we'll communicate using good old-fashioned viewscreens. Truth is, I never liked the holograms. They look too much like ghosts."
- Christopher Pike

"Cheeseburger, fries, habanero sauce."
"You wanna order some lighter fluid with that?"
"That goes with the shake."
- Una Chin-Riley and Christopher Pike

"Sorry, the universal translator sometimes has trouble reconfiguring my lingual clicks and pops."
– Linus, apologizing for translation difficulties

"I had a cold last week, which sucked."
 - Linus, on Saru's rhinovirus

"We're at a full stop, sir. Whatever has us, we're locked into place."
"Like a damn fly in a web."
"And there is the spider..."
- Keyla Detmer, Christopher Pike, and Michael Burnham, upon discovering the Sphere

"Are you saying it's some kind of a lifeform? Maybe it is a damn spider, I hate spiders."
"It is premature to assign any anthropomorphic distinction or intent."
- Christopher Pike and Michael Burnham on the Sphere 

"Welcome to the Tower of Babel."
- Christopher Pike, in Hebrew, as Saru enters the bridge while the universal translator malfunctions 

"Am I the only one who bothered to learn a foreign language?"
- Saru, as the universal translator malfunctions 

"I didn't realize a greenhouse could be critical or propulsive, but what do I know? I'm just a gearhead, not a farmer."
- Jett Reno

"Antimatter and dilithium might be old school, but they don't let you down."
"Why soar when you can crawl?"
"You don't know me, doc. I'm un-insultable, especially by a guy who thinks he can run a ship on mushrooms that I pick off my pizza."
"Spores are clean, renewable."
"Yeah, do they come with house dressing?"
"... Do you have any idea how many planets have been ruined by dilithium mining? How many battles were fought to corner its supply? Of course you don't. You're one of those people who never even considers it!"
"And you're one of those people that does a ha-ha jokey thing, and then gets all huffy and in high dudgeon when you can't think of a comeback."
 - Jett Reno and Paul Stamets, on the merits of the spore drive

"You know, it was only a couple centuries ago that the Earth nearly choked to death on pollution, then we all woke up, and within a generation, everything from a truck to a toaster was covered in solar panels. Yesterday's solar panels are today's fungi."
"Huh... I can fix stuff with duct tape if you want."
- Paul Stamets and Jett Reno

"Do you think May had anything to do with the sphere?"
"What, a giant entity from our universe and a mycelial species from the network? They have as much in common as me and that grease monkey."
"I could fix that analogy with duct tape too."
- Tilly, Stamets, and Reno

"How do I explain to the woman who has fought over and over for the right to take her next breath that I come from a race that submits?"
 - Saru, to Burnham

"Did you record your life before Starfleet?"
"You might say my life began when I was granted refugee status by the Federation. While being processed at Starbase 7, I saw for the first time, lifeforms from across the universe. Some with less than I had, yet with a dream of something better. I listened. Every story I heard created a space inside me to feel more, to love more. I joined Starfleet to help those in need, the way I was helped."
- Michael Burnham and Saru

"Signal's piss poor. We need to amplify it. Cortical implant."
"Wait, you're talking about trepanation?"
"Drilling a hole in her skull? Yeah."
"Are you gonna fix her up with duct tape after?!"
"Maybe."
- Jett Reno and Paul Stamets

"It is so beautiful. The light, it is almost like music."
- Saru, after the Sphere's death

"Your vital signs have returned to normal. How are you feeling?"
"I have never felt this way before. Fear has always been the governing principle of my life. But now... it is gone. More than that, I feel... power. My own power!"
- Tracy Pollard and Saru, after his transformation

"The sphere didn't just give us its language. We have recorded everything it has seen and experienced the last 100,000 years. Its legacy, and your legacy has a new chapter."
"A new and deeply troubling one... The Kelpien way of life had always been oriented toward death and the role the Ba'ul play in it. My people call it the Great Balance. It is our central organizing truth."
"But you proved it wrong."
"Precisely. And you asked me before why I could not go home. It is because I made a promise to Captain Georgiou to uphold General Order 1, not to interfere with the destiny of my species. But now... knowing that what my people have accepted as the truth is a lie... what does this mean for us? For my species? My planet?"
 - Michael Burnham and Saru

 Background information 
 Title 
 The title of this episode is a reference to Greek mythology. An  was the coin placed in the mouth of a dead person before burial as the toll for Charon, the ferryman on the river that divides the worlds of the living and the dead.

 Cast and characters 
 Wilson Cruz and Shazad Latif are not credited as main cast members and do not appear in this episode.
 As of this episode, Rebecca Romijn became the second actor to portray the iconic role of Una Chin-Riley, aka "Number One". Majel Barrett-Roddenberry originated the role in . In this episode, Captain Pike only refers to her as "Number One". Her name was not canonically revealed until the season finale, .

 Music and sound 
 The song sung by Stamets and Tilly in engineering is "Space Oddity", originally by David Bowie but recorded for this episode by actors Anthony Rapp and Mary Wiseman.
 A few musical cues from this episode were released in the soundtrack collection Star Trek: Discovery - Season 2. The first, entitled "The Sphere", plays during the climactic bridge scene at the end of the teaser; the second, called "Quarantined", is audible in the engineering scene in which Stamets and Reno realize that Tilly is under the effect of psilocybin; and the third, named "Shields", can be heard in the bridge scene involving Burnham and Saru persuade Captain Pike that the sphere isn't hostile, as well as accompanying the start of the next scene, leading up to Stamets and Tilly singing David Bowie's "Space Oddity".

 Continuity 
 The stardate is listed on Captain Pike's console, 1834.2512, while he is listening to the sphere's historical data in his ready room.
 Blaming it for the system failures suffered by the Enterprise, Pike orders its holographic comm system ripped out entirely and the viewscreen used for communications instead. This is consistent with , where the holo-communicator is never seen used.
 Una Chin-Riley brings along a PADD with stylus from the Enterprise similar to ones seen in the original series.
 At least a week has passed between this episode and .
 Starfleet has classified Spock's case as Level One, which is highly unusual for a case involving a line officer.
 Louvier is established to have been chief engineer of the  prior to Montgomery Scott taking on the position.
 Almost all of the details about Saru's backstory that were established in  are referenced in this episode.
 This episode reveals that Saru can speak ninety-four languages. He was previously revealed to have learned ninety languages in . It seems that a measurable percentage of these languages are Human languages.
 Saru's quarters include a telescope appearing to be Philippa Georgiou's, albeit now mounted on a tripod. The telescope was bequeathed to Burnham as part of her last will and testament in , but Burnham gave it to Saru in .
 Stamets refers to Humanity's rapid move to solar panels as a response to nearly choking to death on pollution sometime in the past. This seems to mirror Jonathan Archer's reference to a 2061 noteworthy event regarding the use of fossil fuel in .
 In the same dialogue, it is established that dilithium mining causes significant ecological damage to the planet's environment. In , the rainforests of Corvan II are threatened by "industrial pollutants". It was revealed in  that Corvan II was the site of a significant dilithium production.

 Reception 
 

 Production history 
 : Title publicly revealed 
 : Premiere airdate on CBS All Access
 : International release date (outside Canada and the USA)

 Video and DVD releases 
As part of the DIS Season 2 DVD collection
As part of the DIS Season 2 Blu-ray collection

 Links and references 
 Starring 
 Sonequa Martin-Green as Michael Burnham
 Doug Jones as Saru
 Anthony Rapp as Paul Stamets
 Mary Wiseman as Sylvia Tilly
And
 Anson Mount as Christopher Pike

 Guest starring 
 Tig Notaro as Jett Reno
 Rebecca Romijn as Una Chin-Riley  
 Rachael Ancheril as Nhan
 Bahia Watson as 

 Co-starring 
 Hannah Cheesman as Lt. Cmdr. Airiam
 Emily Coutts as Lt. Keyla Detmer
 Patrick Kwok-Choon as Lt. Gen Rhys
 Oyin Oladejo as Lt. Joann Owosekun
 Ronnie Rowe Jr. as Lt. R.A. Bryce
 Julianne Grossman as Discovery Computer
 Raven Dauda as Dr. Tracy Pollard
 David Benjamin Tomlinson as Linus

 Uncredited co-stars 
 Hélène Cardona as a Discovery Engineer 
 Shelley Owens as a Discovery medical crewmember

 Stunt double 
 Dana Jones as stunt double for Tig Notaro

 Stand-in 
 Stacy-Ann Buchanan as stand-in for Sonequa Martin-Green

 References 
; analogy; Andorian language; anthropomorphic; antimatter; Arabic; argon; army ants; aura; Ba'ul; brother; captain; cheeseburger; chief engineer; cold; commander; computer virus; cortical implant; Dead Sea Scrolls; digital antibody; dilithium; ; doctor; doves; drum; duct tape; Earth; electronvolt; English; ; Federation; firewall; first contact; fly; freckle; fredalia; French; French fries; General Order 1; ; German; ; grease monkey; Great Balance; greenhouse; gum; habanero sauce; hallucinogen; harmonic interface; Hebrew; ; holo-communicator; house dressing; impedrezene; Italian; jahSepp; Kaminar; Kelpien; Kelpien language; Kelpien knife; kelvin; Klingon; laser scalpel; library computer; life support; lightning rod; Louvier; Mandarin Chinese; mining; mission statement; multiphasic stasis field; mushrooms; mycelial network; Norwegian; organic transporter; parade; pizza; plasma burn; plasma regulator; power drill; ; psilocybin; quaternary star systems; Red Angel; refugee status; relay junction; rhinovirus; Roquarri Imperium; Russian; salt; ; Saurian language; shield harmonics; shuttle; Siranna; sister; solar panels; "Space Oddity"; spacedock; ; Spanish; spider; Spock; spore drive; Starbase 5; Starbase 7; suicide; Tau Cetian; teleporter; threat ganglia; toaster; Tower of Babel; trepanation; truck; ultraviolet light; universal translator; vahar'ai''; warp core; warp signature; water buffalo; Welsh; Wolof; xenon

Map references 

59 Eridani; Ajilon; Alhena (Gamma Geminorum); Alpha Monocerotis; Amargosa; Archer; B'Moth; Bortas; Buruk; Canopus (Alpha Carinae); Beta Lankal; Beta Thoridar; Cursa (Beta Eridani); Dayos; Deep Space Station K-7; Donatu; Earth; Epsilon Hydrae (Epsilon IV); Epsilon Monocerotis; Epsilon Outpost; Gamma Eridon; Ganalda; Gorath system (Theta Hydrae); Gr'oth; H'atoria system; Halee; Hegh'ta; Ikalia; Iota Geminorum; K't'inga; K'vort system; Khitomer; Klach D'kel Brakt; Klothos; Krios; Mempa; Morska; N'yengoren; Narendra; ; Ogat (star system); Outpost MZ-5; P'Rang; Pheben; Praxis; Psi Cancri; Q'Tahl; Qo'noS; Qu'Vat; Relay Station 47; Rura Penthe; Sigma Geminorum; Sol; Starbase 23; Starbase 24; Starbase 36; Starbase 105; Starbase 117; Starbase 152; Starbase 212; Starbase 234; Starbase 343; T'Cha; T'Ong; ; Toh'Kaht; Toron; Tranome Sar; Tribble Prime; Ty'Gokor; Valt; Veridian; Vor'nak; Vorn;  (Zeta Leporis); Xol; Y'tem

External links 
 
 
 
 

de:Der Charonspfennig
es:An Obol for Charon
fr:An Obol for Charon (épisode)
pl:An Obol for Charon
Obol for Charon, An