12 Monkeys 2015 - 2018 : List of All Seasons

In Season 4, James Cole and Dr. Cassandra Railly set out on an epic quest, traveling further back in time than they have ever been before. According to legend, their only hope lies with a weapon capable of stopping the Witness for good. But they'll soon discover that in order to win the final battle and save time itself, they will have to make the ultimate sacrifice.

Follows the journey of a time traveler from the post-apocalyptic future who appears in present day on a mission to locate and eradicate the source of a deadly plague that will eventually decimate the human race.