Mackenzie needs a vacation, and Ronnie has just the ticket - a luxury sleeper-train voyage through the Rockies. Along with Manny, they pack up and board the West Coast Zephyr in Chicago, ready for five days of peace. The first signs of trouble appear, however, when members of the crew go missing, a true mystery. Relaxation for Mackenzie will have to wait if the train ever wants to reach its destination beyond the mountains, where a howling blizzard waits.