Barnaby and Troy investigate the murder of Gregory Chambers who was killed when out in the woods mushrooming. He was one of four people who had recently inherited a portion of his employer's estate, principally a local hotel. With his death, his one-quarter share now passes to his wife, Suzanna, who has been having an affair with Tristan Goodfellow. It would also appear that Gregory was having an affair with Annie Salter, who is four months pregnant. When Tristan is poisoned with a type of mushroom known as Destroying Angel and the other inheritors of the estate are put at risk, Barnaby looks to find a common connection.