For over 25 years one man has written and received hundreds of letters from some of Britain’s most notorious killers. Pretending to be a woman, he made them fall in love with him. He charmed them into confessing their most hideous crimes. He cajoled them into revealing their true characters and motivations. And now the world’s most iconic criminal profiler has sifted through this new evidence. He’s going inside the twisted minds of the likes of Peter Sutcliffe, Richard Blenkey, Shaun Armstrong, Roy Whiting and Ian Huntley to discover what made them into monsters. So brace yourself and turn on the lights – because it’s very dark and very scary in there.