Doctors, nurses and health workers have a duty of care to their patients to ensure they act in the best interests of an individual; and not act or fail to act in a way that results in harm.
But those featured within these pages are serial killers who roamed their places of work, preying on people at their most vulnerable.
Angels of Death is an updated collection of real life crimes exploring murders committed in hospitals and doctors' surgeries - the very places where lives are supposed to be healed or saved.
The accounts also include cases where the murderers struck in places that are meant to be safe havens, like aged care homes and even people's living rooms.
These disturbing crimes take place in Australia, the United Kingdom, the USA, Canada and Europe.
Emily Webb is a journalist and author, specialising in true crime. She co-hosts the popular podcast Australian True Crime.