Killer Couples

In the first episode, Mark will examine the most infamous killer couple in UK criminal history - 1960s child-killers Myra Hindley and Ian Brady

Episode two will feature John Duffy and David Mulcahy, who - in the 1980s - operated together as two of the most prolific rapists in British criminal history.

The bizarre 1970s case of Roy Hall and Michael Kitto (episode three) is perhaps the most incredible crime story you've never heard of.

Finally in episode four, Mark explores the contemporary case of Lee Whiteley and Deborah Taylor - real-life natural born killers