It was no ordinary gun. It was specially designed to help its owner kill a man. George Mars customized a Colt revolver so it would fire when it was on half cock, saving the time it took to pull back the hammer before firing. But then the gun was stolen from Mars's shop. Mars had engraved his name on it but, as the weapon passed from hand to hand, owner to owner, killer to killer, his identity became as much of a mystery as why possession of the gun skewed the odds in any duel. And the legend of the killer gun grew with each newly slain man.