In their tour of Mexico, Charles and Emlyn arrive at a remote inn in the foothills of the Sierra Madre mountains and a surprise encounter with Lloyd, a friend from Charles' college days. Although their meeting is fortuitous, it also happens that Charles and Lloyd share a common interest in the ancient legend of "El Aguila Negra," the Black Eagle, a Spanish grandee who built the fortress which has since become the guest house of the play. The legend which surrounds him is a tale of murder and unrecovered treasure, and its story is echoed in another unsolved crime which occurred in the same place and under cloudy circumstances just a short while before the action takes place. Adding to the aura of mystery are Laura, a beautiful and taciturn guest from New York; Dr. Anton, the local physician; and Adriana and Daniel, the brother and sister who manage the hostelry. All are, it appears, somehow connected with the most recent murder and all would seem, as well, to provide clues to the untangling of the earlier crime. Charles and Lloyd discuss the limited information available, and Charles becomes convinced that by adding logic where facts are missing he will be able to reconstruct, and solve, both crimes. Charles sets to work in earnest, reluctantly abetted by a timorous Emlyn and then joined by Laura as well. But as the process of reconstruction and reasoning brings the trio closer to the truth, it also draws them ever deeper into danger. The last moments of the play become breathtaking, and the denouement, when it comes, is shattering.
A gripping yet continually amusing study in suspense-filled deduction.