William Cyril Moxley was hanged at Sydney's Long Bay Gaol in 1932 - the first execution in New South Wales for eight years. His crime was the brutal rape and murder of 21-year-old Dorothy Ruth Denzel and the vicious beating and killing of her boyfriend, Frank Barnby Wilkinson. How did this World War I army deserter, small-time thief, conman and police informer come to be the infamous murderer Mad Dog Moxley? Was it simply a robbery gone wrong? Did his blackouts and migraines stem from a head injury as he claimed, or was he the monstrous sociopath described by the prosecution lawyers and the tabloids? Why did he leave such an obvious trail? Would he be found guilty today?