Beverley Allitt worked as a nurse on the children's ward at Grantham and Kesteven Hospital in Lincolnshire in 1991, where over a few weeks she poisoned and injected thirteen children in her care, killing four of them. British newspapers gave her the nickname "The Angel of Death" once the pattern of unexplained cardiac arrests among her patients came to light. This film uses interviews with the investigators and medical staff who worked the case, along with accounts from the victims' families, to walk through how the attacks were carried out and how long it took the hospital to recognize what was happening on its own ward. It sets Allitt's crimes against her diagnosis with Munchausen syndrome by proxy, a disorder in which a caregiver harms the people under their charge in order to be seen as the one who rescues them. The film treats that diagnosis as a partial explanation rather than a full one, leaving the specific mix of psychology and opportunity that let the attacks continue as long as they did an open question.