Under the Andes

Rex Stout

A non-Nero Wolfe novel, rather Wierd Science and pulp magazine-ish. From Goodreads: "Under the Andes is an early novel by Rex Stout, first published in the All-Story Magazine in 1914. Temptress Desirée Le Mire and brothers Paul and Harry Lamar search for lost treasure in a mysterious cave. They encounter Incas who have been deformed by living underground."