Carter O'Brien's gun is for hire, but only when the job - and the money - is right. As tough as they come, he's been everything from lawman to bounty hunter in his time. Right now he's riding shotgun on an expedition led by an old Army buddy. The goal: to find a lost canyon of silver down in Mexico. But the way is blocked not only by gunmen working for a greedy businessman, but also a ghost from O'Brien's past.