The central twist of "Rear Window" is that L.B. Jefferies' suspicions are, in fact, correct: Lars Thorwald did murder his wife. After a series of near-misses and red herrings, including a trip where Thorwald seemingly puts his wife on a train (it was an accomplice disguised as her), the truth is definitively revealed. The proof hinges on Mrs. Thorwald's wedding ring, which Lisa discovers in Thorwald's apartment after he has given away the rest of his wife's jewelry.
The climax sees Thorwald discovering he is being watched. He crosses the courtyard and enters Jeff's apartment, confronting the man who has been spying on him. The suspense shifts from observational to physical. Jeff, helpless in his wheelchair, defends himself with the only weapon he has: his camera's flashbulbs, temporarily blinding Thorwald. Thorwald ultimately throws Jeff out of the rear window, but police arrive in time to save Jeff and arrest Thorwald. In a final ironic twist, Jeff survives the fall but breaks his other leg, ending the film with two casts.
The murder of the neighbor's dog is also revealed to be Thorwald's doing. The dog was digging in the flowerbed where Thorwald had buried a piece of evidence (or possibly part of the body), forcing him to kill it to protect his secret. The resolution of the subplots across the courtyard provides a final thematic summary: Miss Lonelyhearts finds companionship with the songwriter, and Miss Torso's soldier boyfriend returns, revealing the complex realities behind Jeff's initial, superficial observations. The final shot of Lisa switching from an adventure book to a fashion magazine after Jeff falls asleep subtly suggests that their own relationship's conflicts may not be fully resolved, adding a layer of ambiguity to their happy ending.