A look at the hunt for California's Zodiac Killer, who murdered at least five people in the San Francisco Bay Area in the late 1960s and early '70s.

Esther returns to Austria from the United States and a series of murders points to the Zodiac Killer.

The identity of the serial killer known as 'The Zodiac' has been confounding investigators for nearly fifty years, but an unlikely and unconventional theorist may have finally shed light to America's most famous cold case by asking a question that no one else has ever dared ask: what if the reason the Zodiac has never been caught... is because he never existed in the first place?

Soon after his birth-mother contacted him for the first time, Gary L. Stewart decided to search for his biological father. His disturbing identity would force Stewart to reconsider everything he thought he knew about himself.