In this New York Times–bestselling true crime memoir, a man's search for his biological father leads to a notorious American serial killer. When Gary L. Stewart decided to search for his biological father at the age of thirty-nine, he never imagined his quest would lead him to a horrifying truth and force him to reconsider everything he thought he knew about himself. Written with award–winning author and journalist Susan Mustafa, The Most Dangerous Animal of All tells the story of Stewart's decade long hunt. While combing through government records and news reports and tracking down relatives and friends, Stewart turns up a host of clues—including forensic evidence—that conclusively identifies his father as the Zodiac Killer, one of the most notorious and elusive serial murderers in history. Finally, all the questions that have surrounded the case for almost fifty years are answered in this riveting narrative—a singular work of true crime at its finest, as well as a sensational and powerful memoir. THE BASIS FOR THE 4-PART FX DOCUMENTARY MINISERIES