
`World's Most Evil Killers' delves straight into the stories of the world's most prolific killers. Each episode focuses on one notorious killer and features firsthand accounts of their behaviour; such killers range from Fred and Rose West, Ed Gein, the Clown Killer, to the Milwaukee Cannibal. Accounts are also given by detectives who ran the cases, journalists who reported on them, relatives, experts on crime analysis, and sometimes even survivors.

Joanne Dennehy violently stabs three men to death in March 2013; she kills for her own entertainment and is diagnosed as a psychotic sadomasochist.

Stephen Port callously kills four young men between 2014 and 2015.

An examination of the Polish serial killer who came to be known as The Scorpion.

Beverley Allitt killed four children and attempted to murder nine more while working as a nurse at Grantham and Kesteven Hospital in Lincolnshire, England, in 1991.