TimeRiders: Day of the Predator

Liam, Maddy, and Sal are TimeRiders, teens who've been saved from certain death to prevent time travel from destroying history-and the future. But when Maddy mistakenly opens a time window, Liam is marooned sixty-five million years in the past, in the hunting ground of a deadly species of prehistoric predator. Liam's only hope is to make contact with Maddy and Sal before he's hunted down by dinosaurs, and without altering history so much that the world is overtaken by a terrifying new reality.