When she was twelve, Prenna James emigrated to New York City from the future. Hers was a future ravaged by a mutated mosquito-borne plague, and the only survivors have discovered that they must change the past to prevent the plague from even evolving. Now seventeen, Prenna struggles to follow the time-travelers' rules, which state never to become romantically involved with a "time native." However, when Ethan Jarves crosses her path, Prenna desperately wants to break that rule.