One of Our Planets Is Missing (episode)
The Enterprise crew learns that a massive, planet-destroying cloud has entered Federation space.

Summary 
"Captain's log, stardate 5371.3. A huge cosmic cloud has been reported moving into the outer fringe of our galaxy. Nothing like it has ever been seen before. Starfleet Command has sent the  to investigate, as we are the only vessel in the vicinity of the phenomenon. Our present position is in the Pallas 14 system, which contains Mantilles, the most remote inhabited planet in the entire Federation."

As the Enterprise nears the Pallas 14 system, the cloud engulfs planet Alondra, and the planet completely disappears from sensors. Lieutenant Uhura believes that the cloud may have blocked it from being scanned, but Spock reports that the cosmic cloud engulfed it, and broke it up into small pieces in seconds. Captain Kirk asks, "Spock, is it possible that the cloud consumes planets?" Spock answers in the affirmative. Suddenly and without warning, the cloud changes course, heading directly for Mantilles. Kirk orders Sulu have the speed increased to warp 8 in order to intercept the cloud more quickly.

"Captain's log, supplemental. At warp eight, we will intercept the cloud before it reaches the inhabited planet Mantilles, but we are uncertain what we can do to stop a matter-energy cloud which measures thousands of times more than our vessel."

The Enterprise maneuvers itself directly into the path of the cloud and the ship is engulfed. It is pulled into the cloud by streamers made of koinoenergy, an almost ambiplasma with an unusually attractive force. When Kirk gives the order to fire phasers, Spock reports that the cloud seems to be absorbing the phaser energy.

Since it is unknown if the entity has selective abilities, the Enterprise crew assumes that not only Mantilles, but all planets and star systems are in danger. The Enterprise decides to warn Bob Wesley, governor of Mantilles. But before it can do so, the ship is engulfed by the cloud, and unknown objects comprised of highly charged, gaseous antimatter swarm the vessel, causing a large power drain of the shields. An antimatter charge from the shield is successful in dissipating the objects.

"Captain's log, supplemental. The Enterprise has only 15 minutes left before her power is drained and we are left helpless."

Research by Spock indicates that the cloud is actually a living being, and that the objects act like enzymes, slowly breaking up the remnants of Alondra and the Enterprise. After more studying of the creature's anatomy, the Enterprise plots a course through the digestive system, with enormous power consumption. To regenerate the ship's rapidly declining antimatter reserves, Montgomery Scott cuts off a piece of the creature's villi, has Kyle beam it aboard, and uses it to create power regeneration of the ship's anti-matter reserves, with minutes to spare. Kirk sighs, "Scotty, you've just given the Enterprise, and Mantilles, a chance to live." Scott replies, "Thank you, sir." Spock then ascertains the being has a brain and, on hearing this, Kirk plans to use the Enterprises complement of photon torpedoes to destroy the cloud's brain. When Spock begins to remind Kirk of the Starfleet regulations against the killing of intelligent creatures, Kirk stops him, noting that he is well aware of the regulations. But they don't yet know if the cloud is intelligent and it is a fact that every living thing on Mantilles will die, unless they stop the cloud, and so if Kirk is forced to make a choice, he chooses saving Mantilles.

"Captain's log, stardate 5372.0. Spock and Uhura are using our sensors to prepare a detailed chart, so we may determine targets for our photon torpedoes."

Feeling very unsure about his decision, Kirk asks, "Am I doing the right thing, Bones? Once I said that man rose above primitiveness by vowing, 'I will not kill, today." The ever-pragmatic Bones replies, "But you can't let this thing destroy eighty million lives, either." Spock tells them the brain is so vast that the Enterprises entire complement of armaments may not guarantee its destruction. He determines that they would have to destroy the Enterprise itself and direct the explosion right at the cerebral cortex. Kirk orders Scott to prepare the ship for self-destruct and Spock to try to establish contact with the creature.

"Captain's log, stardate 5372.1. The cloud will reach Mantilles in seven minutes. Spock has been working on the mechanics of reaching the cloud's thoughts, but I doubt if there's any time left. And even if we do establish contact, can we communicate with it and persuade it not to kill?"

Spock uses a mind meld to contact the creature and allows the creature to see glimpses of Human life for the first time. The creature comes to understand that its food, the planets, are inhabited by "many somethings, so small, but alive. Comprehend. Not desire to consume other beings." The creature allows the Enterprise to leave peacefully and agrees to depart the galaxy. Kirk asks, "Spock, what did you perceive?" The first officer replies, "The wonders of the universe, captain. Incredible, completely incredible."

Log entries 
 Captain's log, USS Enterprise (NCC-1701), 2269

Memorable quotes 
"It's immense! Twice the diameters of Saturn, Jupiter and Neptune together!"
 - Arex, on the size of the cosmic cloud

"Spock, is it possible the cloud consumes planets?"
 - Kirk

"It is possible this cloud in which we are entrapped is a living thing. The cloud is alive."
 - Spock

"Scotty, you've just given the Enterprise, and Mantilles, a chance to live."
"Thank you, sir."
 - Kirk and Scott

"Am I doing the right thing, Bones? Once I said that man rose above primitiveness by vowing, 'I will not kill, today."
 - Kirk

"Spock, what did you perceive?"
"The wonders of the universe, captain. Incredible. Completely incredible."
 - Kirk, after Spocks mind meld with the cloud (last lines)

Background information

Story and production 
 This episode was written by Marc Daniels, who directed many episodes of Star Treks original series. Gene Roddenberry encouraged him to develop the idea for this episode. "I have to admit," commented Daniels, "that it was different but fun to do some writing rather than just directing." (, issue #114, p. 44) This episode was influenced by Daniels having enormous fondness for the premise of one of the episodes he directed, ; he liked it so much that he transferred many elements in this episode's script from that earlier plot. (These Are the Voyages: TOS Season Two, "The Doomsday Machine")
 Though Bob Wesley was played by Barry Russo in the original Star Trek series, James Doohan provided Wesley's voice for this episode. 
 One of the few sound effects from TOS that is heard in the animated series is featured in this episode: a klaxon that goes off in Chief Engineer Vanderberg's office in , when the Horta steals the pump mechanism from the pergium reactor.
 Most of the shots of Earth, shown to Spock on a computer screen as he is melding with the cloud intelligence, were taken from another  Filmation TV show, . Illustrated by George Wheeler, an animator who otherwise very much wanted to work directly on the animated Star Trek, ultimately became indirectly involved though the contribution of this series of images. (Star Trek: The Official Guide to the Animated Series, p. 46)

Continuity 
 Lieutenant Arex appears for the second time in this episode, and it is the first where he speaks.
 This episode is where we see, for the first time, the Enterprises antimatter nacelles, where Kirk and Scotty use the piece of villi extracted from the cloud-creature to recharge the antimatter engines.
 Kirk paraphrases himself in this episode, stating, "Man rose above primitiveness by vowing, 'I will not kill, today." While this line is never explicitly spoken by Kirk in any previous episode, it does echo the meaning of a speech that Kirk made in , in which he states, "We're Human beings with the blood of a million savage years on our hands, but we can stop it. We can admit that we're killers, but we're not going to kill, today. That's all it takes. Knowing that we won't kill, today."
 In a memo from D.C. Fontana to Gene Roddenberry, dated , reviewing errors she observed in the aired episode, she pointed out that "Governor Wesley of the planet Mantilles is incorrectly shown garbed in Star Fleet Uniform (and the wrong color uniform at that!) when he should have been dressed in civilian clothes."

Reception 
 The editors of Trek magazine collectively scored this episode 2 out of 5 stars (a rating that they termed "fair"). (The Best of Trek #1, p. 109)
 In the unofficial reference book Trek Navigator: The Ultimate Guide to the Entire Trek Saga (p. 161), co-writer Mark A. Altman rates this episode 3 out of 4 stars (defined as "good") while fellow co-writer Edward Gross ranks the episode 3 and a half out of 4 stars (defined as "great"). Altman characterizes the outing as "one of the most interesting" spatial anomaly episodes and goes on to say, "The animation competently conveys the size and shape of the marauding cloud [....] Spock's mind-meld with the cloud is both logical and satisfying, and Kirk and Spock's wrestling with the need to protect life-forms is intelligent and provocative." Altman also remarks on the episode's links to other canon productions, calling the reuse of the Bob Wesley character "cool continuity!" Gross describes the episode as "highly satisfying" and "one of the best the animated spin-off has to offer," also giving kudos to Marc Daniels and saying that the episode "nicely encapsulates" the philosophy of Star Trek.
 In 's "Ultimate Guide" (), this episode was rated 3 out of 5 Starfleet arrowhead insignias.

Adaptation 
 This episode was novelized by Alan Dean Foster in Ballantine Books' Star Trek Log 1 (along with  and ). Additionally, the novelization of  (as published in Star Trek Log 2) references the events of this episode, mentioning "the Mantilles Incident."

Video and DVD releases 
UK VHS release (CIC Video): Volume 2, catalog number VHR 2536, .
As part of the The Animated Series LaserDisc collection.
As part of the The Animated Series DVD collection.
As part of the The Animated Series Blu-ray collection

Links and references

Starring 
William Shatner as Capt. Kirk
Leonard Nimoy as Mr. Spock
And
DeForest Kelley as Dr. McCoy

Also starring 
George Takei as Hikaru Sulu
Nichelle Nichols as Uhura
Majel Barrett as the cosmic cloud
James Doohan as
 Arex
 Montgomery Scott 
 Bob Wesley

Background characters 
 Kyle
 Sciences lieutenant 1
 Sciences lieutenant 2
 Children in archive file

References
2258; aft; Alondra; "all right"; ambiplasma; amoeba; analysis; anatomy; annihilation; anti-kilo; antimatter; antimatter charge; antimatter engine; antimatter nacelle; area; assumption; "at all costs"; "at this moment"; attraction force; audio system; Bezride; body; "Bones"; ; brain; brain core; bull; central core area; chance; chart; chemical identity sensors; conclusion; choice; collie; composition; computer; contact; corrosion; cortex; course; damage; deflector screen (aka deflector shield); diagram; diameter; digestion; digestive system; Earth; element; energy; engineering core; entrance; ETA; evacuation; evasive action; fact; Federation; figure; five thousand children; food; force field box; fraction; Gabler; Governor; grazing; hour; hull; hysteria; indigestion; input; involuntary response; judge; Jupiter; kilometer; koinoenergy; library computer; lifeform; logic; macromorphase enzyme; Mantilles; ; matter; matter engine; Milky Way Galaxy; million; mind; minute; mist; nacelle; navigation scan; Neptune; "no more"; "no problem"; nutrient; object; "of course"; offensive armament; "on the other hand"; opinion; order; organism; origin place; Pallas 14 system; Pallas 14 system's stars; panic; particle; pasture; periodic table; phaser; phaser energy;  phenomenon; photon torpedo; physical contact; planet; population; power drain; primitiveness; priority one call; psychology; quarters; regenerating chamber; remote control; Saturn; second; selective ability; self-destruct mechanism; sensor; sensor range; shape; small intestine; speed; spherical; star; Starfleet; Starfleet Command; General Orders and Regulations; stomach; subspace radio message; synaptic electrical impulse; target; target area; teeth; theory; thing; threat; thought; thousand; time; thought; tractor beam; transporter; truth; universal translator; universe; viewscreen; villi; Vulcan mind touch; wall; ; Wesley's ships

External links 
 
 
 
 

TAS episodes
de:Die gefährliche Wolke
es:One of Our Planets is Missing
fr:One of Our Planets Is Missing (épisode)
nl:One of Our Planets is Missing
pl:One of Our Planets Is Missing