Joe Banks, played by Tom Hanks, is a hypochondriac who has been stuck in a dead end job for years. He sees a series of doctors who all tell him he has a "brain cloud" and only has a few months to live. Joe realizes he has been wasting his life and decides to quit his job. He finally musters the courage to ask his co-worker, DeDe (Meg Ryan), out on a date, but she is already engaged.
Suddenly, a mysterious man named Graynamore (Lloyd Bridges) appears and offers Joe a deal. Graynamore represents a tribe on a remote Pacific island who believe that they can only appease the volcano gods by sacrificing a human. Graynamore offers Joe a huge sum of money to jump into the volcano and sacrifice himself, believing that he would die soon anyway.
Joe reluctantly agrees to the offer and, along with a group of luggage and a trunks filled with personal possessions, he sets off on a journey to the remote island. During the voyage, he meets three different women, each played by Meg Ryan, who influence his outlook on life.
When they reach the island, Joe is greeted by the tribe and they give him a hero's welcome. However, he begins to question his decision and tries to escape. With the help of one of the women he met on the voyage, Angelica (Meg Ryan), they attempt to flee and ultimately, jump into the volcano.
However, they realize at the last minute that the brain cloud diagnosis was false, and Joe decides to live his life and love fully with Angelica. They are rescued by Graynamore and live happily ever after. The film ends with Joe, now cured, standing on a city street corner, excited about the future.