In the season finale, “Praimfaya,” it's a race against the end of the world as Praimfaya arrives forcing our heroes to make impossible decisions to ensure their survival. Eliza Taylor, Bob Morley, Paige Turco, Marie Avgeropoulos, Devon Bostick, Lindsey Morgan, Christopher Larkin, Richard Harmon, Zach McGowan, Isaiah Washington and Henry Ian Cusick star.The 100 have continued to fight for survival. That fight has torn them apart, turned them against each other, and taken the lives of their closest friends. Previously our heroes found themselves at the epicenters of both the Grounder world and the struggle for Arkadia’s soul.
Despite their best efforts, all out war appeared unavoidable until a new, even more dangerous threat, one that had been quietly rising all along, exploded to the surface: ALIE, the A.I. that ended the world, offered relief from pain and eternal life in the “City of Light,” but as her ranks grew, it quickly became clear that she was building an army dedicated to controlling all sentient life on Earth. This was no longer a battle between warring factions; it was a fight for humanity itself. The series is based on the book series by Kass Morgan.