Following a rash of fatal drug overdoses, Da Vinci learns that one of the dead addicts had an infant, who is missing. Manny, a police informer leads Leary, with new partner Angela Kosmo, to the woman's drug dealers. They arrest Todd and Sioux, and through them Larry discovers that the killer heroin came from a French-Canadian supplier who, along with his partner, was murdered, gang-execution style, just days previously.

Patricia Da Vinci's career is on a high when she is asked to be a guest speaker at the prestigious Seattle Homicide Conference. Her presentation involves the recent case of the prostitute serial killer Charlie Josephs, who himself was found murdered. Her re-examination of the case leads to the discovery of several discrepancies and uncovers some new clues in Joseph's death, clues that seem to implicate the police.

Sioux, who is now a police informant for Kosmo, implicates Danny in the drug trade and Kosmo is forced to examine her feelings for him.

Da Vinci investigates the death of man who fell off the roof of his apartment building while attempting to steal cable. Meanwhile Kosmo and Leary uncover a witness in the police beating of a young drug dealer. Later, Zack and Da Vinci uncover some startling news about the mayor.

While Da Vinci remains at odds with the Mayor and Police Chief he attracts attention from Ottawa. Meanwhile, Leary and Kosmo discover that a murdered drug runner was under police surveillance and Shannon's reaction to a personal loss puts his job in jeopardy.

Da Vinci discovers he's the target of a private investigation. Meanwhile, Brian further implicates Sue in the murder of one of his informants.