Dennis Nilsen killed, defiled and dismembered fifteen young men between December 1978 and February 1983, practically under the noses of his neighbors. When police finally arrested him in 1983, it quickly became apparent that, had they linked a series of reported incidents from lucky escapees over the previous five years, they might well have halted his ghoulish killing spree considerably sooner.

Dennis Nilsen was born on November 23, 1945 in Fraserburgh, Scotland. His parent's marriage was an unhappy one and, as a result he lived (along with his mother and siblings) with his maternal grandfather, whom Nilsen adored. Nilsen claimed that his beloved grandfather's unexpected death, when he was just six years old, and the traumatizing viewing of his corpse at the funeral, led to his later behavioral psychopathology.

Quick Facts: In the presence of the tenants, including Nilsen, the technician discovered rotting human remains when he descended via the outdoor manhole.

His mother went on to remarry and have four more children, leaving Nilsen a withdrawn and lonely child. Aware of his homosexual attractions, he claimed no sexual encounters as an adolescent and, aged sixteen, he enlisted in the army. He became a cook, serving as a butcher in the Army Catering Corps, learning the skills that served him so well during his five-year killing spree.

On leaving the army in 1972 he took up police training, where he discovered a fascination for morgue visits and autopsied bodies. Despite the obvious advantages that police work gave to develop his morbid tastes, he resigned and went on to become a recruitment interviewer.

Nilsen's first official brush with the police came in 1973. David Painter, a young man whom Nilsen had met through his work, claimed that Nilsen had taken pictures of him while he was asleep. Painter was so incensed that he required hospitalization as a result of their confrontation. Nilsen was brought in for questioning about the incident, but was subsequently released without charge.

In 1975, he took up cohabitation with David Gallichan in a garden flat situated at 195 Melrose Avenue, in North London, although Gallichan denied that they had a homosexual relationship This lasted two years and, when Gallichan left, Nilsen's life began a downward spiral into alcohol and loneliness, that culminated in the first murder eighteen months later.