'Cold Light of Day' is based on a true story, the life of Britain's foremost mass murder Dennis Andrew Nilsen. Ex Policeman, ex RAF officer, ex Social Security manager and murderer of 17 young men. Through the dark side streets of London Nielsen stalks is prey like Jack the Ripper. Nilsen killed men and boys in gruesome circumstances between 1978 and 1983, and was known to retain corpses for sex acts. He was eventually caught after his disposal of dismembered human entrails blocked his household drains: the drain cleaning company found that the drains were congested with human flesh and contacted the police. Owing to the similarities between their crimes, sexuality and lifestyle, Nilsen has been referred to as the "British Jeffrey Dahmer".