San Francisco in the 21st Century. The City by the Bay's famous fog has become an infamous lethal shroud. A permanent toxic mist that's choked half the population, and now cloaks the sinister doings of a fanatical crime crime syndicate, The Black Angels. You, you're the grittiest hard nosed cop ever to wear an SFPD uniform. And your assignment: descend into the poisonous mist in your XB500 hoverbike, capture the villainous ringleaders, and solve the mystery of the Cloud that kills. Before San Francisco gasps its last breath.