Gretzler: The Silent Serial Killer

He is the serial killer you've never heard of ... until now. In 1973, 22-year-old Doug Gretzler embarked on a cross-country road trip that spiraled into a brutal killing spree. In just three weeks, he and his accomplice, 28-year-old Willie Steelman, murdered 17 people. Their motive? A mystery that has left family members, law enforcement and experts baffled for decades.