Trailer & Synopsis for Season Finale of BOARDWALK EMPIRE This Sunday on HBO

The 12th and final episode of season one for Boardwalk Empire airs this coming Sunday, December 5th only on HBO; Check out a teaser for the highly anticipated episode.

This week's episode saw plenty of set-up for more violence later on and also brought Michael Shannon's character Agent Van Alden's story arc to it's most extreme yet with the murder of a crooked partner Agent Sesbo during a baptism in which Van Alden drowns him in dramatic fashion.

"Sesbo's a little creep. He shot the witness. He's not a good person. Sesbo's an a**hole. I mean, I'm not saying he deserved to die, but he's not an example of a good guy. I don’t think he wanted to kill him, I just think he wanted to baptize him. The kid, he wouldn’t say yes and, you know, Van Alden’s a very angry person and I think when he drowns Sebso, he’s drowning everybody."

"He’s drowning Nucky, he’s drowning this whole situation. Because I think he resents the fact that he’s been put in the middle of so much sin and depravity. I think Van Alden really wants to be a good person, but there’s a lot of resentment and frustration built up inside of him because he can’t — it’s impossible," said Shannon.

In the 10th episode, before Van Alden snaps and actually murders a fellow agent, he resorts to drinking alcohol and has sex with one of Nucky Thompson's (Steve Buscemi) former mistresses. Shannon also commented that he didn't approve of that character arc.

"The thing that disappointed me the most was when he drank. Shooting that episode in general was kind of upsetting. I guess I figured he'd probably drink eventually - I just didn't think it would happen so quickly. In this environment, he can’t maintain his character and his ideals. And so he’s disgusted with himself as much as anybody else … I think the word is he snapped," said Shannon.