Leon, Claire, and Sherry prepare to leave the police station and go to the sewer system, but along the way they encounter the creature with the bulbous eyeball on its shoulder. Wielding a pipe, it attacks them and proves to be a formidable opponent. It begins to attack wildly, and eventually tires before falling over the railing and into the abyss. The bridge collapses from the strain of the fighting, and Leon falls down after him into the sewer. Upon recovering, he finds Ada again. She's trapped in a gun fight with another woman, who calls her a "thief". Ada plans to make a maneuver, and Leon can see she'll leave herself wide open. As Ada moves and the woman takes aim, Leon jumps between them and takes a bullet to the back. The woman runs off, and Ada tends to Leon's wounds. He inquires about the altercation, and senses Ada won't be as forthcoming as he wants her to be. He insists she tell him more, but she reluctantly declines as she views the contents of a familiar looking pendant.
Sherry gets lost in the sewers system, and as Claire looks for her, she finds Leon limping not too far away. Leon explains what happened, and they continue looking for Sherry. Along the way they encounter Trenchy again, and they are forced to defeat him again to move on. They take out zombies, Web Spinners, Lurkers, and other creatures before they arrive in a room with a green pool and a bridge. Suddenly the woman who shot Leon appears, revealing herself to be Sherry's mother, Annette Birkin. Annette also turns out to be the wife of the creature with the bulbous shoulder-eyeball, now called G. G was once William Birkin. In the form of a flashback, Annette tells Leon and Claire how the T-Virus occurred. An Umbrella Special Forces unit led by HUNK tracked down Birkin with the intention of taking his G-Virus research and samples by force. Birkin resists, and they gun him down. HUNK retrieves the sample and departs, but Birkin decides to take his last G-Virus and inject it into himself. Now as a rampaging G-Virus carrier, Birkin kills the entire unit, leaving HUNK as the only survivor. Annette explains that the drive of any G-Virus carrier is to procreate, and Birkin's now primal instincts carried him to the police station, where he killed Ben, and implanted an embryo into Irons. Annette fears that he's after Sherry, due to the fact that he needs hosts that are genetically compatible to him to procreate successfully. Upon realizing they both have the same goal of finding Sherry, they part ways and Leon and Claire move on ahead. They find Sherry, who panics and runs away. Just when things couldn't get any worse, a crocodile infected with the T-Virus appears and attacks them. They're able to defeat it and reclaim Sherry. But things only get worse.