S.T.A.R.S. Bravo Team was sent in to investigate the cannibal murders that were reported in the Arklay Mountains, but suffered engine failure with the chopper and lost contact with the R.P.D. On July 24,1998, Alpha Team was sent in to search for the missing Bravo Team but never came back, except for Alpha Team Pilot Brad Vickers who later resigned.
Raccoon City got hit with an outbreak from a mysterious virus that was turning the citizens into mindless killing machines. The R.P.D. were no match against the hordes of flesh eating zombies and mutants that roamed the street. On the other side of this, a Police officer named Leon S. Kennedy is stuck in the middle of this disaster. Will he be able to survive this nightmare or will he end up like the S.T.A.R.S. members?
There are differences between the Main Series and Dark BioHazard:
In the first Resident Evil, a handful of S.T.A.R.S. members(Jill,Chris,Barry,Rebecca,Brad)survives the Mansion Incident while In Dark BioHazard's storyline, the S.T.A.R.S. Team was completely wiped out. Although Brad is killed by Nemesis in Resident Evil 3, he is the sole survivor of the mansion incident in Dark BioHazard. After which he is awarded the Distinguished Service Medal but refuses, and later resigns from the police force, leaving Raccoon City to investigate on Umbrella Inc.