The year is 2035 and humankind subsists in a desolate netherworld following the eradication of 99 percent of the Earth’s population, a holocaust that makes the planet’s surface uninhabitable, and mankind’s destiny uncertain.

In order to preserve their fate in this grave new world, survivors must rely on time travel as their only hope. Desperately hoping that the resources of the past might help them reclaim and rebuild the future, a group of scientists living beneath the once populous Philadelphia, secure a volunteer to embark on an experimental trip back to the year 1996. There, they hope he can help mankind’s desperate efforts to unravel this apocalyptic nightmare before it completely erases humanity from the planet.

Bruce Willis is Cole, the reluctant volunteer who may not be the ideal candidate to complete this dangerous assignment. However, he possesses a significant trait that supersedes the scientists’ doubts — his obsession with a haunting image from his childhood, a memory whose meaning cannot be understood even though it replays itself endlessly in his tortured mind.

When Cole arrives in 1996, he meets Jeffrey Goines (Brad Pitt), the unstable son of a renowned scientist, and Dr. Kathryn Railly (Madeleine Stowe), a psychiatrist and author who’s expertise lies in the study of madness and prophecy. Railly first diagnoses Cole as delusional; more simply, a madman. However, as their relationship grows, her alarm over his prophetic warnings of the world’s fate turns to conviction, and she comes to believe that mankind may indeed be doomed.

While also questioning his own sanity, Cole struggles with Railly to unravel the mystery with his only two clues: the haunting childhood memory and a series of puzzling symbols from a group known only as The Army of the Twelve Monkeys.