When Miss Jane Marple goes to stay with her frail old friend Carrie-Louise at her sprawling Victorian Gothic mansion which is also a rehabilitation centre for delinquent boys, she gets the increasingly uneasy feeling that all is not well.
When an attempt is made on the life of Carrie-Louise's husband and her step-son is murdered, Miss Marple vows to do all she can to protect her friend and stop any more brutal killings.