The final stage of Dauntless initiation gathers all their fears in a single simulation landscape. All the initiates, including the Divergents, are aware they are under a simulation and must use the skills they've learned in the previous stages to overcome each obstacle. Tris's relationship with Four continues to grow as she prepares for this stage of testing, and he lets her into his own fear landscape. Four has four fears in his landscape, hence his nickname, which is a low number that's rarely heard of. She also learns he is really Marcus's son Tobias, the child of the Abnegation leader the Erudites accused of child abuse. Four shares information he discovered about Erudite's plans to use Dauntless to stage an attack on Abnegation with Tris.