Irene Trent Barbara Stanwyck is unhappily married to a blind, pathologically possessive millionaire inventor, Howard Trent Hayden Rorke. Their palatial mansion is filled with an assortment of cuckoo clocks, all in perfect synchronization, and Howard tapes every conversation in the house, hoping to catch Irene plotting an illicit liaison. Irene lives in a constant state of dread due to Howard's jealousy, faithful not by choice but because he never lets her leave the property and entertains no guests except his attorney, Barry Morland Robert Taylor. Howard spends his days in his upstairs laboratory, working on a variety of projects he refuses to divulge to anyone, while Irene indulges her yearnings for an extramarital affair through recurring dreams of a fantasy lover.
Howard is killed by an explosion in the laboratory, and Irene is set to inherit the house along with Howard's entire fortune upon completion of the probate process. The charred laboratory is secured by a padlock so that no one may enter it. Irene has a nightmare in which a disfigured Howard stalks her through the house. Convinced she must leave the site of Howard's death, Irene moves back into the back-room apartment of the beauty shop she owns, which she operated prior to marrying Howard. There, she finds a confidant in Joyce Judi Meredith, a newly hired beautician.
Irene continues dreaming of her fantasy lover. During one instance, Irene and her fantasy lover are married in front of a group of wax figure witnesses. Irene recognizes the chapel as the same one in which she and Howard were married. Howard himself then enters and is remarried to her, while the fantasy lover disappears. When she awakens, Irene is convinced this latest encounter was not a dream, and visits the now-abandoned chapel with Barry. A groundskeeper allows them inside, and Irene finds the wedding ring from her dream lying on the floor. Irene's fantasy lover watches her and Barry depart the chapel. Barry at first insists that the incident was only a dream and that Irene is losing her sanity due to Howard's death, but abruptly changes his tune and says that a private detective named George Fuller, who Howard hired to stalk Irene, could be playing the part of the fantasy lover.
Later, while visiting the empty Trent home alone, Barry hears Howard's voice. When Irene returns to the beauty shop, Joyce relays an anonymous message from George: "Pleasant dreams." Joyce is stabbed to death in the salon by a man who resembles Howard. Barry arrives at the salon and claims to Irene that Howard also attacked him. Irene and Barry drive to the Trent estate. Barry enters the house while Irene tries to call the police from a pay phone, but the line has been cut.
Hearing gunshots, Irene rushes inside and, in the wrecked laboratory, is confronted by Barry, who shows her he has been impersonating Howard using a prosthetic mask. Barry admits to causing the explosion that killed Howard after writing his own name in as the primary beneficiary in Howard's will. Being blind, Howard did not know he was signing his fortune over to Barry, and Barry plotted to keep Irene from finding out by driving her mad with staged "dreams." George blackmails Barry for half of Howard's estate, and so became a part of the scheme. He tries to kill Irene, since she can be a witness to his crimes. Barry, having a sudden change of heart, fights to save Irene, and the two men fall to their deaths through a gaping hole in the laboratory floor. Looking down on their corpses, Irene breaks into insane laughter.
