The police investigate the death of Colin Doyle who is found murdered sitting behind the wheel of his car. More interestingly they find dozens of passports and ID cards in the trunk of his car. Clearly Doyle was an identity thief and a good one who likely bilked a great many innocent people out of their savings and investments. Dr. Isles' autopsy reveals that the man was killed by by an ice pick. When it's determined that Doyle was actually the son of one of Boston's top-rated and most wanted Irish mob enforcers, Patrick Doyle, the police think it was likely an attempt to flush the elder Doyle out into the open. Maura's examination of the dead man also reveals something completely unexpected - that he is her biological brother. Meanwhile, Frankie Rizzoli arranges a plumbing job for his Dad at their favorite pub - and ends up working with him overnight.