T-Rex: Back to the Cretaceous 3D follows 16-year old Ally Hayden, the daughter of a paleontologist, on a wondrous pre-historic adventure as she is magically transported back through 65 million years to the Cretaceous Period. Here she encounters the largest, most realistic dinosaur ever to appear on movie screens - the 20-foot tall, 15-ton -- Tyrannosaurus Rex.