In 1959, Michael Courtland (Cliff Robertson), a New Orleans real estate developer, has his life shattered when his wife Elizabeth (Geneviève Bujold) and young daughter Amy are kidnapped. The police strongly recommend that he provide the kidnappers with shredded blank paper instead of the demanded ransom, and he agrees to the plan. This leads to a bungled car chase in which both kidnappers and victims are killed in a spectacular explosion. Courtland blames himself for the deaths of his wife and daughter.
15 Years later. Courtland is morbidly obsessed with his dead wife, and regularly visits a monument he has had built in her memory. The monument is a replica of the church (Basilica di San Miniato al Monte) where he and Elizabeth had met many years before in Florence, Italy. His real estate partner Robert LaSalle (John Lithgow) convinces Courtland to tag along on a business trip back to Florence. While there, Courtland revisits the church, and suddenly comes face to face with a young woman named Sandra (Bujold again in a dual role) who looks exactly like his late wife. The already slightly unhinged Courtland begins to court the young woman, and subtly attempts to transform her into a perfect mirror image of his dead wife.
Courtland returns to New Orleans with Sandra so they can marry. On their wedding night, Sandra is kidnapped and a ransom note is left behind by her abductors. It is an exact replica of the kidnappers' message from fifteen years before. This time, Courtland decides to deliver the demanded cash. He withdraws massive quantities of money from his accounts and business holdings, financially ruining him and forcing him to sign over his interest in the real estate business to LaSalle. In the process, he discovers that his entire ordeal, including the original kidnapping, had been engineered by LaSalle as a way to gain sole control of Courtland's company share holdings. The now nearly insane Courtland stabs LaSalle to death.
Knowing that Sandra must have been a willing accomplice in the plot against him, he goes to the airport to kill the escaping woman. On the plane, Sandra has a flashback to her part in the scheme; she is in fact Courtland's daughter, allowed by LaSalle to survive the explosive traffic "accident" from years before that had killed her mother. LaSalle had told her lies about Courtland over the years, convincing her that her father had not paid the ransom because he didn't love her. Sandra, who now loves Courtland, attempts suicide on the plane and is taken off the flight in a wheelchair. Courtland sees her and runs toward her, gun drawn. A security guard attempts to stop him but Courtland smashes the briefcase full of money against the guard's head, knocking him unconscious. The briefcase breaks open and all of the money flies out. Sandra, seeing the fluttering bills, stands up and shouts: "Daddy! You brought the money!" Courtland now realizes for the first time who Sandra really is, and father and daughter fall into a deep embrace.