For a community psychiatric nurse, Monica Morris has an unhealthy interest in poison and when, on impulse, she buys an antique ship's doctor's cabinet with a set of leather-bound journals she becomes fascinated by the content. A few days later, she discovers the body of her patient, Jan Collins… and although police assume suicide by overdose, Monica is not convinced. When more unexplained deaths involving poisoning occur, Monica realises they are linked and so does DS Adams who is investigating. But how are they connected? And why?