The feature-length documentary film about Lucy Letby, the British neonatal nurse who was found guilty of murdering seven babies and attempting to murder seven others under her care, hears for the first time from the British police who investigated the case and features never-before-seen footage of Letby during her arrests and police questioning. The documentary includes interviews with experts and lawyers on both sides, and also includes an AI anonymised interview with a mother of one of the victims, who speaks for the first time about her experience and involvement in Letby’s trial. This group of contributors from both sides make The Investigation of Lucy Letby the most comprehensive look at one of Britain's most notorious crimes.