Complex sentence: 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.
Split into simpler sentences: 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.