Diaz and Andy stumbled on a tough situation this week. They found a mean beaten half to death in an alley. Turns out, through the investigation, the culprit is a fellow detective named Bibby, the partner's of Peck's brother.
When they confront Bibby about this in a bar, he basically admits to beating up the man because the guy stole some (illegal) money from Bibby. He challenged Andy and Diaz to turn him and, saying he'll destroy them if they do - but this doesn't stop the duo! They go to their boss and explain the situation. Having such balls impresses Sam, but it royally pisses off Peck's brother. He tells off Diaz, which may cause a problem down the line since Diaz is dating his sister.
Meanwhile, Traci and Epstein were involved in the case of a girl at a private school overdosing on speed. They were on the scene as part of a community outreach program and this storyline showcased Traci's understanding side. She was often picked on in high school, but overcame those issues to do her job and figure out what was going on.
On the personal front, Andy tried to talk to Sam about their near-sex last week, but he blew it off, saying "it was what it was." He was partly angry because Luke told everyone he was taking Andy away for the night. This also led to an intense confrontation between Sam and Luke during a basic training fighting drill.
In the end, Andy went off with Luke while Sam drank alone at the bar. But the last shot of the episode was Andy alone on the deck of the cabin, staring into the distance, lost in thought.