The team investigates the murder of Petty Officer Peter Karp, who was found dead at a strip club. Karp was apparently always unhappy with the Navy, complaining and moaning about his lot in life. When they learn that the murder weapon, a gun, was also used in two previous unsolved murders, they worry that there is a serial killer on the loose.
They take a look back at the two other victims, but they don't find any immediate obvious connection even when adding Karp to the mix. They learn that Karp only joined the Navy as a way to dodge possible sexual assault charges in college.
Forensic evidence leads them to an overpass that features a soup kitchen run by a local do-gooder, Mama T., and a large decorative mural. They're shocked to discover the names of all three of the murder victims on the mural, along with a fourth man who hasn't yet died.
The fourth man, Kevin Heller, refuses protection. They realize that all the men were suspect and/or got away with terrible crimes. Heller was suspected of killing Mama T.'s son Terrence in an argument over a girl.
The team looks into that case and discover that Heller was only in the area because he was going to a popup gay bar and couldn't have been the man to kill Terrence. When they present Mama T. with this evidence, she breaks down and confesses that one of the local homeless men is the killer taking out the names of those people on the wall as a sort of vigilante justice. They locate the murder weapon when they arrest him.
Brody, meanwhile, has to deal with the return of her ex-fiance, James, and all the emotions that accompany it, which is complicated by the fact that she's now dating psychiatrist Sam Wilkins. James is only stopping over briefly in New Orleans and leaves again after sharing one night of passion and an intense kiss.