The narrative centers around Chris Redfield, who serves the BSAA alongside the military in a mission to hunt down Glenn Arias, a notorious global arms dealer who has obtained a deadly biological weapon: a new zombie virus. During their operation, Chris' team suffers devastating losses, and Arias reveals a horrific truth—he has turned Chris' undercover agent friend into a zombie capable of distinguishing between allies and enemies.
Months later, we find Rebecca Chambers, a former member of S.T.A.R.S. turned scientist, diligently researching the new virus in her lab. Just as she makes a breakthrough, her facility comes under attack, resulting in everyone but her being transformed into zombies. Fortuitously, Chris arrives to rescue her, and they exchange crucial information. Rebecca discovers that the new virus comprises three essential components: the base virus, a trigger virus, and a cure vaccine. Having tested the vaccine on herself, she remains unaffected and generously provides Chris with a blood sample to aid their cause.
However, their respite is short-lived as Arias' henchmen launch an assault and abduct Rebecca. It's then revealed that Arias survived a catastrophic wedding explosion that claimed his wife and family. He kidnaps Rebecca due to her striking resemblance to Sarah, his deceased spouse, intending to recreate their wedding. When she vehemently declines, he forces an advanced version of the zombie virus upon her.
Chris uncovers information from Rebecca's laptop that points to Arias' next target: New York. He teams up with Leon Kennedy to avert the impending outbreak. With their combined efforts, they succeed in thwarting the crisis. The duo then locates Arias in his hideout, where they find him poised on the rooftop. A fierce battle ensues, and Chris quickly dispatches Arias, but he rapidly recovers, transforming into a monstrous creature.
In a desperate struggle, Chris injures this monstrous version of Arias. However, the situation escalates when one of Arias' most formidable goons sacrifices himself, merging with Arias to amplify his strength. Chris and his team engage in a fierce aerial battle, deploying an energy weapon from their Osprey. This enrages Arias, causing his heart to pulsate ominously.
In a climactic confrontation, Arias lunges toward the Osprey, but Leon outmaneuvers him by launching his bike, detonating the fuel tank in a spectacular explosion. Ultimately, Chris and Leon bring an end to Arias, obliterating his monstrous heart in the process, ensuring that their mission—though fraught with peril—concludes with a hard-won victory.
