Sister Sister is the tenth episode of the sixth season.
A show-dog owner is killed in her backyard. Everything point to the dog being the killer. The two daughters of the woman are the main suspects due to their jealousy of the dog.
- Angie Harmon as Jane Clementine Rizzoli
- Sasha Alexander as Dr. Maura Dorthea Isles
- Lorraine Bracco as Angela Rizzoli
- Bruce McGill as Vincent Walter Korsak
- Jordan Bridges as Francesco "Frankie" Rizzoli, Jr.
- Idara Victor as Nina Holiday
- Adam Sinclair as Kent Drake
- Liesel Allen Yeager as Tricia Evans
- Myra Turley as Delores Cope
- Erin Way as Sara Evans
- Reggie Gaskins as Animal Control Officer
- Michael Lanahan as Eric Hikeler
- Loanne Bishop as Mona Evans
- Cody Chappel as Hipster