In 1911 two British heiresses, Claire and Dora Williamson, read a brochure about a revolutionary fasting treatment that promised a lifetime of good health. The sanatorium in the village of Olalla, west of Seattle, was surrounded by a beautiful forest, sparkling waters and fresh air. The sisters agreed it sounded perfect and exactly the restorative holiday they needed. But within a month of arriving, under the supervision of Doctor Linda Burfield Hazzard, Claire and Dora began to realise the frightening truth – they were not patients but prisoners at the isolated sanitorium.

In October 2014, after Chris Regan failed to arrive at his new job, his ex-girlfriend filed a missing-person report. Something was off. It was not like Chris, a devoted father, avid hiker, and all-around great guy, not to show up. When local Michigan police chief Laura Frizzo learned Chris was having an affair with Kelly Cochran, a married coworker, suspicion fell on her husband, Jason. After a search warrant on their house revealed several suspicious items, the Cochrans abruptly moved to Indiana. As questions swirled around the case, the whereabouts of Chris Regan remained unknown.

On the morning of July 18, 2014, 41-year-old Florida State law professor Dan Markel dropped his boys off at preschool, hit the gym, and headed home to his quiet, tree-canopied neighborhood. Within seconds of pulling into his garage, two .38-caliber bullets fired from point-blank range were lodged in his brain. His brutal slaying defied explanation.

On the beautiful island of Jersey, the wealthy Newall family were the epitome of success: Roderick, the eldest son, was a handsome Royal Green Jackets lieutenant, and his younger brother, Mark, was a financier. On the night of 10 October 1987 Nicholas and Elizabeth Newall went out to dinner with their sons to celebrate her 48th birthday. It was the last time that the parents were seen alive. Sometime during that evening, they were bludgeoned to death at their home, their bodies removed, leaving only bloodstains behind.

Dorothy Davis and Kerry Whelan were both happy, healthy, affluent, middle-class women from conservative, loving families. Such women are hardly ever among the ranks of the missing. They were not hitchhikers, or associates of drug dealers, or unhappy with their family relationships, or suffering from mental health issues. Dorothy Davis and Kerry Whelan came from different parts of Sydney, mixed in quite different circles, and led completely different lives.