On December 30th, 1970, at the age of 38, former heavyweight champion Sonny Liston died from what Las Vegas police suspected was a heroin overdose. When police arrived, they found a one-ounce balloon on Sonny's nightstand but the coroner quickly labelled Sonny's passing as death by natural causes. To this day, Liston's death hovers over Las Vegas and the sports world, leaving unanswered questions about his ties to powerful boxing promoters, billionaire hoteliers, mob kingpins and shadowy drug lords. Reviving boxing's most infamous cold case to work out what really happened on that night in December over 40 years ago, Shaun Assael examines the last mysterious year of Liston's life against the backdrop of a pivotal year in the history of Las Vegas.