Lewis and Kellerman's investigation of a murder in a housing project puts them at odds with a civilian-patrol group, run by the Black Muslims. Munch is excited because Stan is scheduled to come back June 1st. Russert and Munch catch a case where both the victim and shooter are dead. She with Howard must decide whether to circumvent the so-called ""blue wall of silence"" among police officers when it is discovered that the officer on the scene didn't react in time. Barnfather stops Lewis and Kellerman's charging of a Muslim, until something is leaked to the newspapers. The ""big man"" is scheduled to come to the bar, but changes his mind, twice.

Bayliss has disappeared again as Pembleton and Brodie make their way to the scene of a shotgun suicide. The victim appears to be Beau Felton. Gee's letter, including information gained in the ""Burundi"" case, begins to make an impact at the highest levels of the department. Frank returns to the department with the news about his case. Lewis goes off, wondering who is going to be next. Det. Falsone comes to the squad with news about why he thinks Beau Felton killed himself. Lewis and Stivers discuss the Mahoney shooting. Cox finds something interesting about the Felton case; she digs in deeper and the results change the case to a murder. Bayliss turns up the next day and disappears again to his Uncle George's place. Pembleton and Howard try to work with Falsone to find Beau's killer. Gee finds out that Beau had been working undercover for the past six months on the Cantwell auto-theft ring. Megan Russert returns from France.

Mike and Julianna wake up the morning after a night of drinking and passion. The investigation into Beau's death continues; Howard wants to be the primary while Frank tries to maintain control. Gee asks her to step aside and let him do the job with a more unbiased approach. The investigation creates some unlikely pairings: Pembleton with Gharty and Bayliss with Falsone and Munch on his own. Meanwhile, Howard and Russert make arrangements for Beau's funeral. Lewis and Kellerman's investigation into a homicide is stalled; when Kellerman's hangover laden police work is shoddy. When it appears as thought the investigation is going nowhere; Kay demands to be put on the case. Gee refuses. Because of his bad day and finding Julianna drinking with someone at the Waterfront Bar, Kellerman suggests that they should stop drinking. Frank tries to call Mary; eventually they connect and reconcile; with Frank saying that he is willing to give it all up. They find out who killed Beau, but when they go