Over two grim nights in Los Angeles, the young followers of Charles Manson murdered seven people, including the actress Sharon Tate, then eight months pregnant. With no mercy and seemingly no motive, the Manson Family followed their leader's every order. Twenty years ago, when journalist Tom O'Neill was reporting a magazine piece about the murders, he worried there was nothing new to say. Then he unearthed shocking evidence of a cover-up behind the "official" story, including police carelessness, legal misconduct, and potential surveillance by intelligence agents.