Martin Clunes and Keeley Hawes star in this made-for-TV crime drama based on the true story of the 1940s serial killer John George Haigh. After mistakenly believing a Latin term to mean that murder can only be proven with the evidence of a body, Haigh (Clunes) discovers a way to get rid of potential victims by using sulphuric acid. He first kills his friend, Donald McSwan (Neil McKinven), in order to assume control of his business, but in order to increase his finances Haigh takes a number of further victims. When those who knew the deceased become suspicious a criminal investigation is launched and it looks as though Haigh's murderous ways will finally be put to a stop.