Vanessa Ferlito

Warning: Working on the TV series Graceland may be hazardous to your health. That is, if you're Vanessa Ferlito.

"Let's put it this way — by the end of the shoot I had an ulcer," she tells Ferlito, of course, is taking about the jaw-dropping end of last week's episode. After Charlie found her informant, Whistler, dead on the bathroom floor during an important drug bust, she was forced to inject heroin herself since Whistler could no longer vouch for her and Briggs (Daniel Sunjata). "It picks up from right after she shoots up," Ferlito says of Thursday's episode (10/9c, USA). "It's a mess. She's a mess."

So how will picking up the needle affect Charlie long-term? Considering her past use of Vicodin, it won't be so easy for her to walk away unscathed.  "I don't think she can just walk away from a drug like that. I think it would be almost impossible," Ferlito says. "Once you try it, I have to believe that you might go back."

Watchlist: Add all the new fall shows now!

Sadly, Ferlito is all too familiar with the power of addiction. "I've never done drugs, but drugs have affected my life because my father died of a heroin overdose when I was 2 years old," she says. "It could have been any of the other actors and it was me. Maybe they knew that about my past and they knew that would hit a sensitive spot and that I would go there."

Although Ferlito was worried about her mother's reaction to the story line — "she still never gets over when I die" — the actress dived head-first into the role. "My makeup artist would say, 'Wow, you're in that mood today. Oh, right she's preparing for this scene,'" Ferlito says. "I think I do it without even knowing it because I get so worked up about it and so nervous so I feel like, until the end of shooting, I was in a kind of a not a dark place, but you know you have to kind of be in that mind frame without really knowing or experiencing it."

Throughout the process, Ferlito had a valuable source of knowledge about the subject — a Graceland crew worker who is a former heroin addict whom she logged many hours with.  "I asked, 'What would happen the first time? Would I nod out? How would I feel? Would it be euphoria?' I wanted my face to be the right way. So it was pretty intense. I wanted it to be real and I wanted it to be right," Ferlito says. "He says it's a struggle every day. I don't know I'm the polar opposite. I take Tylenol and I sleep for 20 hours. I tried my best."

Watch full episodes of Graceland

Sadly for Ferlito's character, Charlie, her best wasn't enough. Whistler's death last week during the bust will prove to be a major low point for her. "She feels guilt. She feels like it's her fault. She put him back in that position when ... she knew he wasn't ready to be in a position ," she says. "She becomes obsessed. You'll see. To the point where Briggs is like, 'You have to stop.' She's just not going to let it go."

Briggs will play an important role in what's to come for Charlie, especially after their almost-but-not-quite romantic reunion — which came as a shock to some members of the team and millions of fans who had no idea that they ever had been together like that. "And then they have to stop themselves. These poor people — they're tortured souls. They can't even let out their frustrations that way because there will be consequences and they're not going to go back to that place," Ferlito says. "They've come so far and they have a good flow in the house. They're like the mother and father of the house."

Ferlito says learning of Charlie and Briggs' past was a welcome addition to her character's backstory. "It was in the pilot and then they changed it and it was sort of like Charlie and Mike, and then they changed it and brought it back to Charlie and Briggs, but I'm happy because I wouldn't have wanted to do that with anyone else," Ferlito says. "He's such a gentleman and a nice guy. That stuff is never really comfortable."

Daniel Sunjata and more TV eye candy

Ferlito says there's just one downside to sharing a steamy make-out scene with Sunjata. "I talked to him yesterday and I was like, 'You ruined my life,'" she says with a laugh. "People don't ask about me anywhere. They're like, 'Oh I love you, yeah, yeah, yeah, how's Briggs?' The women just go mad for him."

Contrary to their tight bond off-screen, Ferlito and Sunjata's on-screen dynamic will prove to become increasingly complicated, especially because of Mike's discovery last week that Briggs used to be an addict and may be skimming a portion of the heroin seized in cases. "Briggs has a lot going on behind the scenes and you start to question how genuine he is and if his love is real or he's just on a mission to get things done. You don't really know. I think Briggs loves Charlie. They have a very, very intense connection.  But I think when sh-- starts to hit the fan, he starts to push her off as much as possible to steer her in a different direction but she's not stopping. So that definitely puts a strain on their relationship. By the end of the season, it's just like, 'Oh no, will they ever get past this?'"

These characters and these relationships brought Ferlito brought to television after having left CSI: NY early in Season 2. "It isn't your typical procedural. It's about the characters, not just the crime scenes. It sort of reminded me of 24 meets The Real World," she says. "And there's more to come with the characters. You don't really know Charlie's backstory so there's so much more to build on."

Graceland airs Thursdays at 10/9c on USA.