Prime universe
(Capcom's primary storyline)

The 1st Investigation Unit was an Umbrella team sent to the Arklay Mountains to investigate the employee training facility[1] that was closed twenty years earlier.

Their mission, commanded by William Birkin[1] and Albert Wesker,[2] was to make an evaluation of the facility for possible re-opening.[1]

This team explored the facility, uncovering evidence of violations by Dr. James Marcus, condeming at least twenty students to death through his experiments.[3] One member concluded that the viral outbreak in the Arklay Mountains was caused deliberately.[4] The team was attacked by leeches in the building,[3] as well as "things" in the woods[4] - the latter may be attributed to the loose Cerberus pack, who had killed and eaten several people in the mountains previously. The team was made of Umbrella inspectors and armed mercenaries (named Soldiers and Guards in the Investigator's Report 2). It is possible that the many infected mercenaries were either the remains of the 1st team or simply dead Security Force guards.



  1. 1.0 1.1 1.2 Resident Evil 0 (2002), file: "Investigation Orders".
  2. Resident Evil: The Umbrella Chronicles (2007).
  3. 3.0 3.1 Resident Evil 0 (2002), file: "Investigator's Report".
  4. 4.0 4.1 Resident Evil 0 (2002), Investigator's Report 2".