During the film, Jefferies, a photographer confined to a wheelchair due to a broken leg, passes his time by observing the lives of the people who live across the courtyard from him. He begins to suspect that Thorwald has murdered his wife and sets out to prove it, enlisting the help of his girlfriend Lisa Freemont (Grace Kelly).
As Jefferies and Lisa gather more evidence and Thorwald becomes increasingly desperate, the tension builds. The film reaches its climax when Thorwald discovers that Jefferies is onto him and tries to kill him. Jefferies manages to escape and Thorwald is cornered by the police.
The movie ends with Jeffries recovering from his ordeal, and a happy ending for him and Lisa.