Confined to a wheelchair with a broken leg, a professional photographer passes the time by spying on his neighbors through his window. His rear window overlooks a courtyard and other apartments, and with the help of his binoculars and telephoto lens, he observes the daily lives of his neighbors, including a struggling composer, a middle-aged couple with a small dog, a dancer he nicknames "Miss Torso," a single woman dubbed "Miss Lonelyhearts," and a salesman with a bedridden wife. Boredom leads to fascination as peering into the personal lives of his neighbors becomes a daily ritual. He is attended by a no-nonsense, blue-collar home care nurse, who disapproves of his voyeurism, and a sophisticated, high-society girlfriend, who is at odds with his cynical attitude toward relationships.

The photographer's harmless pastime takes a dark turn when he begins to suspect that the salesman may have murdered his wife. After observing a series of suspicious events, including the salesman making late-night trips carrying his sample case, cleaning a saw and large knife, and tying up a trunk, he is convinced a crime has been committed. With his leg in a cast, he is unable to investigate himself, so he enlists the help of his nurse and girlfriend. Together, they begin to piece together evidence, attempting to deduce the truth about the supposed foul play from their limited vantage point. The photographer's intense scrutiny leads them deeper into a mystery that unfolds under the gaze of his rear window.