The squad tries to solve a homicide case that is muddied by conflicting evidence; Maura must decide if she is going to take in her recently paroled grandfather; Jane and Casey must decide between their careers and their relationship.
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The team has two homicides which, at first, seem unrelated. Mark Cabot is killed in the parking garage of a fitness club. Rhonda Clark is drowned in her hot tub. A german shepherd's hair is found in Rhonda's lungs, believed to be from the killer's dog. Connections are made. The team thinks that Mark's sister killed Rhonda and Rhonda's husband killed Mark as part of a murder pact, but see Mark's wife arrive when a sting is arranged for them. Meanwhile, Maura is asked via correspondence from Paddy Doyle to take care of his paroled father, Patrick. She is curious to learn about her heritage, but Patrick wants nothing to do with her. He also believes Paddy wants him to die as a "nobody", but Jane tells him that Paddy might have wanted his father to see the one good thing the son accomplished—Maura. Casey returns home to tell Jane he has been made a full colonel and he must now decide to stay in the service to be a general or retire and marry her.
- Angie Harmon as Detective Jane Rizzoli
- Sasha Alexander as Dr. Maura Isles
- Jordan Bridges as Officer Frankie Rizzoli, Jr.
- Lee Thompson Young as Detective Barry Frost
- Bruce McGill as Detective Vince Korsak
- Lorraine Bracco as Angela Rizzoli
- Brian Goodman as Sean Cavanaugh
- Chris Vance as Casey Jones
- Mackenzie Astin as Professor Rick Clark
- Kelly Kruger as Jenny Cabot
- Heather McComb as Leslie Cabot
- Richard Herd as Patrick Doyle, Sr.
- David Blue as Peter Kaufman
- Celia Finklestein as Professor Rhonda Clark
- Mary Jo Catlett as Bunny
- David Figlioli as Prison Guard
- Betty Murphy as Shirley