December 23, 1952. A transcontinental train is stopped cold by a rockslide in a remote Colorado canyon. There's a murderer aboard, one who has already killed, and will kill again unless stopped. The California Zephyr, with its run from Oakland to Chicago and back, was famous for its Vista-Domes, which provided a 360-degree view of spectacular Western scenery. It was a kind of small city populated by passengers from all walks of life and a large crew whose duty it was to keep them safe. Zephyrette Jill McLeod is the passengers' primary point of contact. She's armed for any emergency with a first-aid kit, a screwdriver, and her knowledge of human nature. But can she figure out a ruthless killer's clever plot in time?