For three days each summer, couriers from around the world descend upon the streets of San Francisco to drink beer, outrun the SFPD, and generally raise hell in a series of unsanctioned bike messenger street races. These races, known as alleycats, are infamous for brutal hill climbs, complicated tasks and testing the limits of even the most hardcore couriers—no wonder it all ends in Sparks, Bud, and illegal fireworks.