Letty 'spins out' in the season 2 finale of Good Behavior 

Letty \'spins out\' in the season 2 finale of 

Letty (Michelle Dockery) has just crossed a line.

’s second season, the con woman who always said she’d never commit a murder committed two. After Teo (Juan Riedinger) cornered her alone in the fancy new home Javier (Juan Diego Botto) just bought her, Letty shot him before he could kill her. But when an innocent security guy (Brian Baumgartner) showed up unannounced and caught her with the gun, Letty fired on instinct, turning a case of self-defense into something a lot more complicated.

“Letty has very definitively said for all the bad things that she does, killing will never be one of them,” co-creator Chad Hodge tells EW. “And then now she has killed not one but two people within the span of 10 seconds. So she has a multitude of reactions very quickly, which — I’ve never been in this position, but it feels like it would be realistic for your mind to sort of spin out a little bit.”

As seen in the exclusive clip above, one of those reactions is to hallucinate the security guy as he may have been in life. Hodge teases that as the plot of the finale “deals with getting rid of these bodies, the emotional plot is Letty battling her own morality with herself in the form of the dead security guy.”

But while the executive producer felt it was important for Letty to do the one thing she said she’d never do, her dark spiral in the past few episodes wasn’t just a means to bring her to this point.

“In episodes 7 and 8,” Hodge says, “that backslide — she gives Jacob back to her mother, then she runs away from Javier and starts drinking and doing drugs and going down that whole bender to where she ends up blacking out in the middle of the woods — was something I really wanted to do, the writers and I, because in telling a story about an addict, we really hadn’t seen that yet with Letty. And I felt like it was time to show what that’s like and how she can deep dive so quickly. Coming out of that, it was always the design to have her kill Teo.”

As for the security guy, Hodge says, “That was a thing I came up with pretty late in the game. The last two scripts were really good, but they were feeling to me a little bit straightforward. If Letty had just killed Teo, he’s like the bad guy. It’s self-defense. We want him dead. Great. It’s good but it’s sort of just not that surprising. So then we built in: Oh my god, they shouldn’t have to just get rid of one body, it should be two. And it should be just some random innocent person because Letty wouldn’t feel that bad about just killing Teo. But she feels really bad about killing this innocent person.”

And it sounds like fans can expect this ordeal to affect how Letty relates to Javier. “Letty, since she’s met Javier has given him s— about being a hitman and killing people and how bad it is,” Hodge says. “It’s like the one moral leg she has to stand on all the time: You kill people so, between the two of us, I’m better than you are. And now, of course, it’s like, well, we have to have her kill someone.”

’s season 2 finale airs Sunday at 10 p.m. ET on TNT. Check out the exclusive preview clip above.