Michael Guider was born on October 20, 1950, in Australia. His childhood was marked by instability, emotional neglect, and abuse. He and his younger brother, Tim, were placed into state care at a young age due to their mother’s inability to properly care for them. Guider showed early signs of social detachment and developed a deep obsession with Aboriginal culture, history, and spirituality, which would later blend into his personal writings and activities as an adult.

In adulthood, Guider worked various jobs including as a gardener at a hospital and a part-time photographer. He gained access to children by offering free babysitting services and by being part of community groups. Despite appearing helpful or trustworthy on the surface, Guider was already abusing numerous children behind closed doors, often drugging them with sleeping pills and photographing them in disturbing positions.

On August 19, 1986, 9-year-old Samantha Knight disappeared after school in Bondi, New South Wales. Her case sparked a massive nationwide search, with posters, media coverage, and public campaigns — but no trace of her was ever found. For years, the mystery haunted Sydney, and Guider remained undetected.

It wasn't until 1994 that police began investigating Guider after a victim came forward. His home was searched, revealing thousands of disturbing photographs of drugged children, confirming years of sexual abuse. He was charged in February 2001, later pleading guilty to manslaughter on 7 June 2001—citing an accidental overdose from drugging, and disposal because he didn’t want her identified . On 28 August 2002, Guider received a 17-year sentence with a 12-year non-parole period, concurrent with his abuse convictions. 

While in prison, Guider eventually confessed to the killing of Samantha Knight. He claimed to have accidentally killed her by giving her too many sedatives (Temazepam) to keep her quiet while molesting her. He said he panicked, placed her body in a dumpster, and it was likely taken to a landfill. In 2003, police excavated near Kirribilli following Guider’s claim that he’d moved Samantha’s body from Cooper Park, but nothing was found—the canine’s reaction suggested human remains may once have been present. 

Guider remained a model prisoner, but was violently attacked in Goulburn Prison twice—and ended up hospitalized .He was denied parole in 2014, 2017, and 2018. Finally, under a strict supervision order, he was released on 5 September 2019, wearing a tracking device, with 56 conditions restricting his activities. In September 2022, police found child abuse material on his phone—he was charged with supervision breaches and re-incarcerated. Guider died on 7 September 2024, aged 73, at Prince of Wales Hospital.