Vultures in the sky / Todd Downing ; introduction by James Sallis.

Enhanced descriptions from Syndetics:

The journey of the Mexico City-bound Pullman seems ill-fated from the outset ? what with the engine troubles and the threat of an impending railway strike ? but no one aboard expects the terror that will descend upon the luxury train between Laredo and its destination. First a man dies as the vehicle passes through a dark tunnel and then, just as United States Customs Agent Hugh Rennert begins to investigate, the train comes to a screeching halt in the middle of the desert.

More deaths follow as night falls, and when it becomes clear that a murderer is on the loose, the stationary cars transform into an isolated hall of horrors. The varied and intriguing cast of passengers begins to panic, but Rennert remains calm and collected, untangling the web of motives in a desperate search for the culprit. Will he be able to unmask the killer before the voyage ends?

A suspenseful whodunnit that charts a path through the Mexican wilderness, Vultures in the Sky highlights the best aspects of the Golden Age mystery, mixing classical detective work with a tense, closed-circle setting. The third novel in Todd Downing's Hugh Rennert series (which can be enjoyed in any order), it shows an undeservedly forgotten author working at the top of his craft.