The tourist
(Book)

"It's expected to be an excursion like any other. There is nothing in the records to indicate that anything our of the ordinary will happen. A bus will take them to the mall. They will have an hour or so to look around. Perhaps buy something, try the food. A minor traffic incident on the way back to the resort will provide some additional interest--but the tour rep has no reason to expect any trouble. Until he notices that one of his party is missing. Most disturbingly, she is a woman who, according to the records, did not go missing. Now she is a woman whose disappearance could change the world." -- jacket.