Setting: 1997, roughly 1 year before the destruction of Raccoon City.

Two years before the Raccoon City outbreak, the older Claire Redfield, a gifted engineering student and amateur investigator, uncovers evidence linking mysterious disappearances in the Arklay Mountains to secret biological experiments conducted by the powerful Umbrella Corporation. Determined to expose the truth, she infiltrates an Umbrella warehouse and steals critical research data, but during her escape she is infected by an experimental virus. As her condition rapidly worsens, Claire entrusts all of her evidence to her younger brother, Chris Redfield, revealing that Umbrella is preparing to recruit her into a specialized engineering program that could provide access to its hidden operations. After Claire dies from the infection, Chris discovers that Umbrella still believes she is alive and continues monitoring her activities. Realizing that Claire's death would end her investigation and allow Umbrella to erase every lead she uncovered, Chris secretly buries his sister and assumes her identity, using his unusually strong resemblance to her to infiltrate the corporation in her place. What begins as a temporary deception evolves into a dangerous double life as Chris, posing as Claire, uncovers deeper layers of Umbrella's conspiracy, investigates the experiments beneath the Arklay Mountains, and becomes entangled in the events leading to the Spencer Mansion incident. When the zombie outbreak finally consumes Raccoon City, Chris finds himself trapped inside the collapsing city while still living as Claire Redfield, forced to maintain the impersonation amidst the chaos as he struggles to survive, honor his sister's final wish, and expose the truth behind Umbrella's bioweapons before countless lives are lost.