A vicious and mysterious predator terrorized Northern California for more than ten years, committing 50 sexual assaults there, before making his way south and committing 10 cruel killings. Then he vanished, evading the attention of numerous law enforcement agencies and some of the greatest detectives in the region. Three decades later, the vicious psychopath known as "the Golden State Killer" was still at large, and true-crime journalist Michelle McNamara, who founded the well-known website TrueCrimeDiary.com, was desperate to catch him. Michelle combed through police reports, spoke with victims, and ingratiated herself with the internet groups that shared her obsession with the case.