Utilising a dangerous and untested method of time travel, a man from the post-apocalyptic future, James Cole, travels to the present day on a mission to locate and eradicate the source of a deadly plague that will decimate the human race. But as he and virologist, Dr Cassandra Railly, track the mysterious cult behind the outbreak, the "Army of the 12 Monkeys," the effects of time travel threaten to destroy humanity's last hope.