An Arcadian Death — Roderic Jeffries

In the isolated Canegot Valley on the languid isle of Mallorca, Spain, miserly spinster Dona Beatriz Ruig is found dead in her bedroom, doors and windows locked from the inside. The arrogant local police officer, Inspector Garicano, naturally concludes accidental death: How could anyone have murdered her without access to the room? But a car accident forces him to turn the case over to a colleague before it's closed.
"You are quite certain that the facts are straightforward? There's not the slightest risk that a person of somewhat limited intelligence who possesses a delight in confusion might try to hold otherwise?" Superintendent Salas asks. Thus our beloved Inspector Enrique Alvarez is assigned to finish the investigation. But apparently the superintendent hasn't heard the saying, as most Mallorcans have, that, "It is easier to make a fool of a wise man than a simpleton." Inspector Alvarez attacks this impossible crime, his eighteenth case, with his usual (if sun-soaked and sleepy) vigor.