The main character, Beatrice, is a member of the selfless community, Abnegation. Her and her 16 year old brother have to decide which faction they want to be part of for the rest of their lives. To help them decide, they undergo a simulation that is meant to tell them which faction they are at heart. Beatrice finds out from the simulation that she is "Divergent", meaning that she actually has characteristics of multiple factions.
Initiate rankings determine whether one gets to remain a Dauntless member or be banished from society.
After finding out that she is Divergent, part of Erudite, Abnegation, and Dauntless, Beatrice decides to become a Dauntless member and change her name to Tris. She undergoes an extremely difficult initiation in which they learn to fight and face their fears in lifelike simulations.
After hearing of an uprising of the Erudite, brainwashing the Dauntless to fight for them and kill all of Abnegation, Tris manages to avoid being brainwashed because she is Divergent and defeat the evil powers.