We finally get confirmation that Jimmy and Mommy have a really screwed up relationship as we learn why he fled off to war and left college. His mom is seriously screwed up and she gets turned on by her son beating up his professor. This continues a weird dynamic in the show where every women except Angela seems drawn to violent men. Margaret obviously knew (or strongly suspected) Nucky had her husband killed before hooking up with him, and even Van Alden's wife got turned on by him beating up a waiter.
Margaret is full of contradictions andhypocraciesas she is feeling guilt over being in Nucky's world and being with the man that killed her husband. Although he continues to deny it, she knows and the guilt of being with a man that murdered her kids father is turning her into a wreck. I don't know where they can go with her, as they already tried theschemerroute with her and her character has developed in a way where she is incapable of just being evil and choosing this life.
On the flip side, Nucky also seems to strongly suspect she cheated with his irish hentchman, and the fact that the maid, who was also involved with Owen found out probably means that its going to come out.
Finally, Van Alden gets caught for the murder of his prohibition agent friend and he is disgraced and on the run. His story might also be coming to an end.
It looks like there is going to be some new characters next season as Lucy, Angela, Van Alden, The Commodore and maybe even Margaret seem to have their stories coming to a close. Like all episodes before a final, this one set up the season final, so how the final turns out will determine how "good" this episode was.