Boston Strangler Redux - S1-E2
Continuity mistake: At the morgue, Dr. Isles is trying to help Frost overcome his fear of dead bodies by having him cut into a body. Rizzoli walks in and Frost turns away from the body. He hands the scalpel to the doctor, with the sharp end pointing down. Cut to the next shot and now the knife has turned around and its sharp end is sticking up. (00:20:45)