Unable to sleep, Elaine Wheeler paces the living room of her Manhattan townhouse, troubled by unsettling memories and vague fears. Her husband tries to comfort her, but when he steps away for a moment Elaine screams as she sees the body of a dead man in the window across the way. The police are called, but find nothing except an empty chair.

From this point on, the plot moves quickly and grippingly as those involved—Elaine's old friend and house guest Blanche; the inquisitive and rather sinister man who lives next door; and the nosy German maid Helga—all contribute to the deepening suspense and mystery of the play as it draws towards its riveting and chilling climax.