Adopted as a baby, Gary Stewart always fought with his identity and after 39 years, the search for his biological parents shows a truth he could not have imagined.

Learning that his father may have been the Zodiac killer, Gary brings The New York Times best-selling true crime author Susan Mustafa in to help uncover more information about him.

Gary's tale takes a turn when he sees his novel could be a betrayal of his new relationship with his true mum and when he faces a group of Zodiac fanatics with ulterior motives, he shows new details that have never been shared.

Provided with DNA evidence that connects his father to the Zodiac killer, Gary forges ahead to uncover his truth and the questions that have tormented him for decades come to a head in a surprising end.