Hyams got Paramount to buy the rights and set about writing a screenplay. He felt the train in his film should be traveling through country "so forbidding that you can't just jump off and go to a rent-a-car counter" so he decided to set the action in Mexico or Canada. "So I took the train through the Rockies and was unprepared for how beautiful it is," said Hyams. "It was the most extraordinary scenery I've ever seen." So he decided on Canada.