The Umbrella Chronicles' first scenario, based on the events of Resident Evil Zero, follows STARS operative Rebecca Chambers, and former Marine Billy Coen as they venture through a train that eventually takes them to a derelict training facility. Once within the facility, they discover they are being stalked by James Marcus, one of the Umbrella Corporation's co-founders and former scientists, who has managed to resurrect himself with the aid of leech test-subjects. After a confrontation, Marcus mutates into a monstrosity, but is subdued by the duo. Chambers and Coen escape as the facility self-destructs. Another sub-chapter within the scenario traces Wesker's actions, now posing as the leader of STARS' Alpha team, as he attempts to escape the training facility. This chapter also introduces Sergei Vladimir and one of his bodyguard Tyrants, codenamed "IVAN".