The true story of the pursuit and capture of Charles Cullen one of the most prolific serial killers in history who is suspected of murdering up to 400 patients during his 16-year career as a nurse earning him the title "The Angel of Death". Cullen was a married father who was thought to be a responsible caretaker before he was implicated for the deaths of as many as 300 patients over 16 years spread across 9 hospitals in New Jersey and Pennsylvania.