The film follows Tris Prior (Shailene Woodley), Tobias “Four” Eaton (Theo James), and their friends as they venture outside the walls of post-apocalyptic Chicago to discover the truth about their society.
In the climax of the movie, Tris and her friends reach the Bureau of Genetic Welfare, a scientific facility that created and monitored the experiment in Chicago. They learn that the factions were an experiment to produce genetically pure individuals, and the Bureau has been watching the citizens of Chicago for generations.
Tris discovers that she is genetically pure, a Divergent, which makes her valuable to the Bureau. However, she becomes suspicious of the Bureau’s intentions, especially when she learns about their plan to use the genetically pure individuals to restore the population outside Chicago.
In the resolution, Tris, Four, and their friends decide to resist the Bureau’s plan. They release a memory serum to erase the memories of the Bureau’s personnel, disrupting their control over the experiment. Tris sacrifices herself by exposing herself to a death serum in order to secure the release of the memory serum.
Tris’ sacrifice leads to a confrontation between her friends and the Bureau, and the movie ends with the characters contemplating the future. The film concludes with a sense of rebellion against the oppressive forces of the Bureau, setting the stage for the fourth and final installment, “Ascendant.”
In summary, “Allegiant” ends with Tris sacrificing herself to disrupt the Bureau’s plans, her friends resisting the Bureau’s control, and the promise of further rebellion in the concluding chapter of “The Divergent Series.”