The theme is the coming to a head of Ray's hiring of Sully to kill Ray's father Mickey. Although the logic of television went against the removal of Jon Voight and his inspired performance as Mickey, the build-up to how Sully was a gunshot away from killing Mickey, and how Mickey managed to dodge that, was both harrowing and brilliant.
It was also poetic. Roseanna Arquette's Linda was spooked in the previous episode, when the ever wanting to be helpful Mickey took Linda literally when she told him a gun would need to be put to her head. In 1.10, she calls him, the two get together for a roll in the hay, she's about to leave - even though incredible Mickey tells her he'd be good for another roll in 20 minutes - when Sully and his thug break in. Before long, Linda's qualms about drawn guns are realized, when Sully shoots her dead in the brush.
Ray was quietly agonizing about his order to kill Mickey - though Abby noticed - and I had thought there was a 50/50 chance that he'd be the one to rush out of the gym and stop Sully from doing it. I was glad I was wrong, because Ray's inaction in these circumstances makes him a more dangerous and interesting character. So, as it turns out, Mickey has to rely on his own smarts to save his hide, which entail his directing Sully to kill Sean Walker for the killing of Colleen, which is what - as Mickey realizes - Sully cares most about.
Why Sully didn't turn around kill Mickey after Walker was dispatched is an open question. Possibly Sully was so grateful that he finally got his satisfying revenge for Colleen that he just let Mickey walk after Walker was sent walking through the pearly gates. But Sully doesn't seem to be the type that overly acts on his gratitude, so there is likely more of a story yet to be told here.
As it is, Ray, who earlier indicated to Abby how much he wanted another baby, is left looking at Walker's smiling baby, as Walker lays dead in the next room. Another piece of dark poetry in this brooding drama which is increasingly finding its unique voice.