On Australia day, 26 January 1966, Jane, Arnna, and Grant Beaumont were abducted from Colley Reserve, Glenelg, South Australia, and never seen again, leading to one of Australia's most extensive police investigations and manhunts. Five decades later, no trace of the children has ever been found.

Over the years, several individuals have been put forward and investigated as suspects, resulting in false leads and dead ends and with no real suspect, until now: Harry Phipps.

On the surface, he was a gentleman: generous, charismatic, and intelligent—a person of wealth and influence in the community. However, a dramatically different person resided behind the walls of his Glenelg mansion, located a mere 190 metres in direct sight of Colley Reserve.

In Unmasking the Killer, author Stuart Mullins (The Satin Man: Uncovering the Mystery of the Missing Beaumont Children (co-author), Joe Bugner: My Story (author)) and former South Australian police detective Bill Hayes expose Harry Phipps as the prime suspect in the abduction, disappearance, and likely murder of the Beaumont children.

Over 10 pieces of circumstantial evidence linking Phipps to the Beaumont abduction are explored in detail, supported by geographic and predator profiling chapters, which detail how these monsters operate. The authors explore a potential link to the 1973 Adelaide Oval abduction of Kirste Gordon and Joanne Ratcliffe and reveal conversations with Haydn Phipps, the eldest son of Harry and a possible eyewitness to events on that fateful day.

Stuart and Bill answer the question: where to next? Along with other experts, they firmly believe the answer to this baffling mystery lay buried at Castalloy, a factory once owned by Harry Phipps.