James Marcus is one of the founders of Umbrella and the main antagonist of Resident Evil Zero. Years before the events of the first Resident Evil, Marcus, along with Ozwell E. Spencer, was one of the founders of the Umbrella Corporation. In his personal journal, Marcus notes that he played an integral role in developing the T-virus through extensive research with leeches; however, Spencer betrays Marcus by sending his subordinates, Albert Wesker and William Birkin, to murder Marcus and steal his research.