Tris and Four are now fugitives on the run, hunted by Jeanine, the leader of the power-hungry Erudite elite. Racing against time, they must find out what Tris's family sacrificed their lives to protect, and why the Erudite leaders will do anything to stop them. Haunted by her past choices but desperate to protect the ones she loves, Tris, with Four at her side, faces one impossible challenge after another as they unlock the truth about the past and...

Sixteen-year-old Cassie Sullivan is trying to survive a world devastated by the waves of an alien invasion, while trying to save her five-year-old brother Sam from a training camp that was created by the Others (the aliens).