One crime baffled a small Argentina town; the other held the entire state of California hostage. The thread that links these two cases occurring 100 years apart: both murderers were done in by their own hand. Specifically, by their fingerprints. Witness the breakthrough moment in 1892 when fingerprinting was first used to track down a child killer and see how the evolving science helped thwart a coldblooded serial killer a century later. Then follow the bloody trail of a serial killer dubbed the Night Stalker and discover how detectives nabbed him with powders, hand-held lasers, and a stroke of luck.