He looked like the friendly neighbor everyone trusted. A soft-spoken civil servant with a kind smile, Dennis Nilsen appeared anything but dangerous. But behind the closed doors of his North London flat, he harbored some of the darkest secrets in British criminal history. Between 1978 and 1983, Nilsen lured young men into his home, where he murdered them—and kept their bodies hidden for weeks, even months, before disposing of them in ways that shocked the nation.