On a cold day in 1983, a plumber was called to an apartment building in the Cranley Gardens neighborhood of North London. The building drains were clogged. And when he climbed down into plumbing "man hole" he saw what was causing the blockage: human flesh and bone. What followed was essentially an elaborate confession by one of the building's tenants: Dennis Nilsen who explained to the police that he had murdered and dismembered at least 12 men and boys and disposed of them both UNDER HIS FLOORBOARDS AND DOWN THE DRAINS. How is it possible that at least 12 people could vanish and be murdered and nobody noticed?