Four (Tobias Eaton)

Four is one of Dauntless's instructors, quiet, serious and hard to impress. The nickname comes from the number of his fears, far lower than anyone else's. Theo James plays him with a cold look that hides care. He came to Dauntless from Abnegation and rarely speaks of the past. That makes him a mystery to the initiates, who don't know why such a capable instructor doesn't seek a higher post. Four prefers to watch and to help when he sees someone needs it, and that is how he grows close to Tris.

Four teaches the Dauntless initiates and has a hard reputation. He notices Tris from the building jump, when she picks a new name, and starts helping her. In the fear simulations he shows her what he dreads, and she learns his real name, Tobias Eaton, and that his father, Marcus, abused him. When Erudite takes over Dauntless, Four pretends to be controlled until he is found out. Tris has to bring him back.

On the run with Tris, Four tells the Factionless he is the son of Evelyn, their leader, the mother who left him with a violent father. He holds a grudge, but she proposes an alliance against Erudite. In Candor the truth serum forces him to speak about himself. Four kills Eric to save Tris, is captured and risks everything to rescue her when Peter helps him. Between his mother and Tris, he chooses Tris.

Beyond the wall, Four trains alongside Nita and soon distrusts the Bureau. On a rescue mission he notices that children are taken and their memories wiped. He tries to warn Tris, but David interrupts. Four asks her to go back to Chicago with him, and she chooses to stay with David. When Matthew tells him David ordered his death, Four fights the soldiers and has to go back to warn Tris.

Tobias is the alternating narrator of Allegiant (2013). Veronica Roth's collection Four (2014) gathers five of his stories: his past, his choice of Dauntless and the nickname. Details in the "What changed on screen" tab of the books saga.