Sam Wheat and Molly Jensen are deeply in love. Their history together is full of happy memories, vacations, photographs and now a newly shared apartment in Brooklyn -- they can't afford Manhattan! 

Sam is a high powered banker who has control of numerous accounts and millions and millions of dollars. He works with Carl Bruner, a good friend who comes round to the apartment and shares take-aways and beers with Sam and Molly. Molly is an artist, often working from home, hence the need for a large loft apartment. Perhaps the only downside to their idyllic existence is Sam's inability to tell Molly that he loves her, only ever using the word "ditto."

Out together one night, Sam and Molly are set upon by a mugger, intent on stealing Sam's wallet. Sam offers him money, but this is not enough for the mugger, Willie Lopez, who is fixated with the wallet, which we later learn contains the passwords to the accounts which Sam has control of. In the struggle that ensues, a shot rings out. As Sam staggers away from Willie, he notices that Molly is crouched desperately over a body. His body. Sam's body is taken to hospital, where he dies on the operating table.

Sam's ghost is stuck between worlds, confused and alone, until he is befriended by a friendly ghost who explains about his current situation. Sam begins to learn how the spirit world works, but he cannot do the one thing that he needs to do, which is communicate with Molly. 

Sam finds himself at the parlour of Oda Mae Brown, a dodgy psychic who specializes in conning money out of vulnerable widows. He realizes that Oda Mae can hear him and he persuades her to visit Molly. Initially cynical, Molly begins to believe Oda Mae when she tells her privates things about her life with Sam. However, in the background, Carl is determined that Molly should not believe Oda Mae.

Sam follows Carl to the flat of Willie Lopez, believing that he is going to confront him, only to discover that the mugging was at Carl's instigation, with the purpose of obtaining the passwords and transferring money from Sam's accounts to his.

Molly finds it harder and harder to cope with Sam's loss and, despite Carl's best efforts to her her forget her fiance, Molly sinks further into her grief. Meanwhile, Sam is working to thwart Carl's plan. With the help of a ghost on the subway, he learns how to move objects with the power of his mind, before beginning to haunt Carl, typing to word "murderer" onto his computer screen. Of course, Carl does not see Sam, so is traumatized by this turn of events. 

Sam persuades Oda Mae to help him once more, this time to become a fictitious account customer, the owner of an account that Carl has created as part of his scam. As "Rita Miller," Oda Mae enters the bank and makes a withdrawal, with Sam giving her pointers to stop her real identity being revealed. Oda Mae can't believe her ears when she is told that she is about to withdraw $10 million and leaves, somewhat unsteadily, with a bankers cheque made out to this amount. Oda Mae considers what she is going to do with her newfound wealth, but Sam makes her give the money away.

They return to Molly, just in time before Carl arrives, desperate for the cheque that "Rita Miller" has withdrawn. In the struggle that ensues, Carl dies and is consumed by the shadows of death. Sam and Molly realize that is is time for them to say goodbye for the last time. Sam thanks Oda Mae and, for the first time, is able to tell Molly that he loves her, before ascending up into the light of happiness and eternal life.