When the family began to show intermittent signs of poisoning during the early part of 1961, Young’s father initially suspected that Young might be inadvertently harming the family by the careless use of his chemistry set at home, but Young denied the accusation. The potential for deliberate poisoning was never considered, especially as Young had also been ill on a number of occasions. It remains unclear whether this was by design (to avoid detection), thorough scientific interest in his own reaction, or just carelessness of exactly which teacups he had poisoned.
When Young’s elder sister, Winifred, was found by doctors to have been poisoned by Belladonna in November 1961, Young’s father again suspected him, but took no action. Molly Young, his stepmother, became the concerted focus of Young’s attentions, gradually becoming more ill until finally, on 21 April 1962, she was found by her husband writhing in agony, in the back garden of their home, with Young looking on in fascination. She was rushed to hospital, where she died later that night. Her cause of death was determined as a prolapse of a spinal bone and she was cremated (not surprisingly at Young’s suggestion), with no further action taken at the time. It was later discovered that she had developed a tolerance to the antimony with which Young was slowly poisoning her, and he switched to thallium the night before her death to speed up the process. There were even reports of further nausea and vomiting attacks at her funeral: clearly the death of his stepmother had not dulled Young’s scientific curiosity.
Following Molly’s death, Fred Young’s attacks of vomiting and cramping became more frequent and increasingly severe, and he was also admitted to hospital, where he was diagnosed with antimony poisoning. He was lucky to have survived his son’s experimentation, but could not countenance his son’s responsibility: that role fell to Young’s school chemistry teacher, who contacted the police when he discovered poisons, and copious material about poisoners, in Young’s school desk.
Young was sent to a police psychiatrist, where his encyclopaedic knowledge of poisons soon became apparent, and arrested on 23 May 1962. He admitted the poisoning of his father, sister and school friend, Williams, but no murder charges were brought against him for the murder of his stepmother, as any evidence had been destroyed at the time of her cremation. Still only 14, he was committed to Broadmoor maximum-security hospital, the youngest inmate since 1885, for a minimum period of 15 years.
Incarceration barely dampened his enthusiasm for experimentation, and within weeks the death of an inmate, John Berridge, by cyanide poisoning, had prison authorities baffled. Young claimed to have extracted cyanide from laurel bush leaves, but his confession was not taken seriously, and Berridge’s death was recorded as suicide. On other occasions, staff and inmates’ drinks were found to have been tampered with, including the introduction of an abrasive sodium compound, commonly called ‘sugar soap’, used for preparing painted walls, into a tea urn that could have caused mass poisoning had it not been discovered. He continued to read widely about poisoning, although he began to keep his obsession increasingly well hidden, when authorities made it clear that appearing less obsessed would speed up his release.
By the late 1960’s Young’s doctors seemed oblivious to his continued fatal fascination and recommended, in June 1970, that he be released as he had been ‘cured’. Young celebrated by informing a psychiatric nurse that he intended to kill one person for every year he had been in Broadmoor; the comment was recorded on his file but, amazingly, never influenced the decision to release him.
When Young was released on 4 February 1971, now aged 23, he went to stay in a hostel but had contact with his sister, Winifred, who had moved to Hemel Hempstead following her marriage. Despite having been poisoned by him, she was more forgiving than her father, who initially wanted nothing to do with his son. She was concerned by his fixation with his crimes: he took great delight in visiting the scenes of his past crimes, thriving on the reaction of his old neighbours in Neasden when they recognised who he was.
He made trips to London, where he stocked up on the antimony, thallium, and other poisons required for his experiments, and a fellow hostel resident, 34-year-old Trevor Sparkes, was soon exhibiting the familiar cramps and sickness associated with any proximity to Young. Another man he befriended experienced such agony that he took his own life, although no connection to Young was established at the time.
Young found work as a store man at John Hadland Laboratories, a photographic supply firm in Bovingdon, Hertfordshire, where his new employers were aware of his Broadmoor stay, but not his history as a poisoner.  They might have had some reservations, given the easy availability of poisons such as thallium, routinely used in photographic processes, but Young had, in any case, already secured his poison supplies from unsuspecting London pharmacists. His willingness to make tea and coffee for his co-workers raised no concerns, so when Young’s boss, 59-year-old Bob Egle, began to experience severe cramps and dizziness, it was attributed to a virus thought to be doing the rounds, known locally as the ‘Bovingdon Bug’, which had afflicted a number of local schoolchildren. Other Hadland workers complained of similar cramps, but none were ever as severe as Egle’s who, curiously, seemed to recover when off work ill, but instantly became sicker than ever on his return to work. He was eventually admitted to hospital where he died, in agony, on 7 July 1971. His cause of death was recorded as pneumonia.
In September 1971, 60-year-old Fred Biggs began to suffer similar symptoms to Egle, and general absenteeism at Hadland increased dramatically, with employees suffering a variety of unusual and debilitating ailments, including the usual cramps, hair loss and sexual dysfunction. Various sources were considered, including water contamination, radioactive fallout and leakage of the chemicals used at the firm itself, but no real progress was made towards the cause.
Biggs was eventually admitted to the London Hospital for Nervous Diseases, but took a long time to die, a cause of some frustration to Young, who recorded his displeasure in his diary. But he eventually succumbed, on 19 November 1971, in excruciating pain.
This second death raised great concern within the firm: by this stage about 70 employees had recorded similar symptoms and there were fears for personal safety. The doctor on site tried to reassure staff, by insisting that health and safety rules were being strictly adhered to, and was taken aback when Young challenged him in front of colleagues, quizzing him on why thallium poisoning had not been considered as a cause, considering that it was used in the photographic process. The doctor was surprised at the in-depth toxicological knowledge espoused by Young, and brought it to the attention of the management, who in turn alerted the police.