Unable to sleep, Elaine Wheeler paces the living room of her Manhattan townhouse, troubled by unsettling memories and vague fears. Her husband John tries to comfort her, but fears for his wife’s mental health.  John calls in a psychiatrist, who agrees with his suggestion that Elaine should commit herself to a sanitarium for treatment. But is Elaine really on the verge of a nervous breakdown, or is someone setting her up?  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.