Professional photographer L.B. "Jeff" Jeffries is a prisoner of sorts in his own apartment sporting a hip cast from one of his adventures. He has little to do and spends much of the time observing his neighbors, including a newlywed couple, a middle-aged woman who lives alone and a ballerina who seems to attract men without much effort. He becomes particularly interested in one neighbor, Lars Thorwald, a traveling salesman whose invalid wife spends much of her time in bed. When he sees Thorwald make several trips out of his apartment on a particularly rainy night, he begins to wonder what may be going on. The disappearance of his wife makes him think he may have murdered her. Jeffries has few visitors, but the elegant and beautiful Lisa Fremont, who is madly in love with him, sees him daily and while she is at first skeptical, soon comes around to his way of thinking. In order to get proof however, it will be necessary for her to enter Thorwald's apartment.