Vultures in the Sky (Hugh Rennert Mysteries)

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.