When Quintero (Fernando Rey), a Mexican revolutionary leader, is left to rot in jail by the forces of President Diaz, it's up to his subordinate, Max (Reni Santoni), to bust him out. With $600 in hand, he crosses the border into America and hires Chris Adams (George Kennedy), a mercenary of considerable skill, who uses the rest of the cash on more hired guns. After the team is rounded out by experts on close-combat fighting, explosives and knife-throwing, they set off to free Quintero.