Ever since the death of her husband, Ursula Ottway has lived alone in Back Rigg Cottage, high up on the fells. Her landlord, the ambitious politician Marcus Grenville, wants his property back. After months of harassment, Ursula discovers that the illegal use of poisoned bait on Grenville's land has killed not only a rare bird of prey but her two beloved cats.
Outraged, Ursula storms up to the Grenvilles' house and denounces Marcus Grenville and threatens revenge. But when her niece, Molly Palmer-Jones, arrives at Ursula's house the next morning, it is to find her body slumped lifeless on a sofa. It soon becomes clear that hers was a very convenient death. The Palmer-Joneses embark on a murder investigation....