For three seasons, The 100 have fought to survive. That fight has torn them apart, turned them against each other, and taken the lives of their closest friends. In season three, our heroes found themselves at the epicenter 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.