Susanna Reid gains access to police evidence from the investigation into Joanne Dennehy, one of Britain's most notorious serial killers. Over two weeks in 2013, the then 30-year-old Dennehy murdered three men and attempted to kill two others, becoming one of only three British women ever to be sentenced to spend the rest of her life behind bars. Five years on from Dennehy's conviction, Susanna speaks to the lead detective, the father of her two children and relatives of victims to provide a picture of how an intelligent and privileged young woman transformed into a dangerous psychopath.