Mr. Campion's Falcon: Albert Campion #21

Mr. Campion’s final adventure points (like so many good mysteries) to the past, as first an archeologist is murdered and then a geologist disappears. The latter has a motley crew of friends, all ham-handedly eager to help. Mr. Campion with his inquiries, and there’s also a supremely dastardly villain on hand. It’s a pity to say farewell to the estimable Albert, but he leaves on a high note indeed