(Capcom's primary storyline)
The Caucasus outbreak occurred in February 2003 in and around the Caucasus Laboratory in the Caucasus mountain range of southern Russia. One of the final Umbrella-specific outbreaks, this event set a chain of events in motion which led to the final shut-down and dissolution of Umbrella. The initial events are comparable to the bizarre incidences in the Arklay Mountains five years prior.
During the events of the "Mansion Incident" and the subsequent Raccoon City Destruction Incident in 1998, Umbrella paramilitary head Colonel Sergei Vladimir moved certain special projects from the Spencer Mansion to the Caucasus facility - namely, the T-A.L.O.S. project and the Red Queen computer. After the destruction of Raccoon City, Vladimir was named head officer of Umbrella by Oswell E. Spencer, who went into hiding soon after.
At the end of January, a t-Virus infected wolf, a result of the nearby Umbrella laboratory, began hunting nearby, and attacked several villagers. This villagers, in turn 'zombified' and infected more villagers. A little girl, Anna, was hid in a wardrobe by her father after her mother transformed. After ensuring his daughter's immediate safety, Anna's father retreated to the village silo, where the adults barricaded themselves inside. Unfortunately, they soon realized they had sealed themselves inside with the infected, and quickly perished. The village chief, armed with a shotgun, chose to freeze to death hiding in a refrigerator over fighting and being eaten.
After two days, only Anna was left alive. By this time the wolf had been captured and Chris Redfield and Jill Valentine drove to the village in a HUMVEE to investigate. Finding the village deserted except for Anna, they soon encountered Albert Wesker, who informed them that the town was like Raccoon City, sponsored by Umbrella. They were attacked by Hunter δs, and Wesker took the opportunity to escape and attempt to find information about the nearby Umbrella Facility. Jill and Chris finally caught up to him in Anna's home, as her father was an Umbrella employee.
Wesker failed to obtain the data he sought due to a booby-trap set by Anna's father, but he managed to obtain blueprints to the facility, while Chris and Jill figured that the nearby facility was one owned by Umbrella.
Caucasus Laboratory Outbreak
Sometime later, Albert Wesker leaked information to the Private Anti-Biohazard Service about the location of the T-A.L.O.S. project. Having discovered the location of Sergei Vladimir, he intentionally released the t-Virus into the Caucasus facility, infecting 98% of the research staff and releasing many of the B.O.W. experiments. As Wesker infiltrated the facility, a special ops squad from the unit, led by Chris and Jill, invaded the facility from the other side.
Wesker was confronted by Sergei after making his way down the main cable car shaft; Sergei commanded his twin Ivans to attack as he made his escape. Wesker managed to defeat the Ivans, and confronted Sergei at about the same time as Jill and Chris reached the T-A.L.O.S. project. In two simultaneous battles, Wesker defeats Sergei whom injects the virus into himself and mutates, while Chris and Jill manage to destroy T-A.L.O.S. (curiously, Sergei offers commentary during the T-A.L.O.S. battle, despite being busy battling Wesker). After, Wesker managed to copy the entirety of Umbrella's computer information onto a single disc, and wipes the Red Queen's memory, while Chris and Jill evacuated the facility, unaware that Wesker had been there also.
Shortly after the Caucasus outbreak, Wesker leaked the contents of Umbrella's unsavory research and business dealings, while anonymously testifying against Oswell E. Spencer. With Umbrella out of the way, Wesker sets his sights on the acquisition of Las Plagas, to take place in the following year, hoping to craft his own Umbrella.