Dinosaurs are very much alive - at least in the mind of Ally Hayden (Liz Stauber). But the closest she has come to them in her world is in seeing the dinosaur bone skeletons and artists' renderings in the museum where her father, the world-famous paleontologist (Peter Horton), has his headquarters.

Like her father, Ally is fascinated by the way that modern science, and the study of dinosaur bones and fossils, can lead to uncovering the mysteries of what dinosaurs were really like - what they looked like, how they moved, how and what they ate and how they raised their young. But while Ally would love to accompany her father on his dinosaur digs, she has to settle for giving tours as a museum guide, and bringing her own theories about dinosaur evolution to life in her science project.

When Donald Hayden and his assistant Elizabeth (Kari Coleman) bring his latest discovery back to the museum, Ally is excited that the oblong-shaped fossil rock might be a Tyrannosaurus egg, finally giving proof to the theory that the enormous theropod dinosaur was an evolutionary precursor to today's birds, and would therefore have exhibited parental behavior. Donald is not so quick to jump to that conclusion, but before he can complete his discussion with his teenage daughter, he is called away from his office.

Ally is alone and waiting for her father to return when an accident in the museum lab mysteriously sets her on an adventure in which Ally's present world begins to meld with the deep past. As she wanders into the museum, the bones of the T-Rex skeleton suddenly appear to grow skin and muscle and the extinct creature lunges to life. When Ally retreats, she is hurtled through time, backwards to the terrain and territory of dinosaurs that are bigger than her imagination.

Finding herself in a strangely lush environment, Ally is awestruck by a herd of thirsty Hadrosaurs drinking at a glacial lake. Continuing to explore, Ally thinks she has found her way back to the modern day museum when suddenly the Deinonychus dinosaurs in a painting by Charles Knight (Tuck Milligan) jump to life. But this time, the famous 1920s-era dinosaur illustrator himself appears in front of Ally and she gets an easel-side audience with Knight, and the opportunity to ask and see how he created his imaginative renderings.

Ally's world seems to shift again when she finds herself in the early 1910s on a paleontology exploration with Barnum Brown (Laurie Murdoch), the most famous bone hunter in history. Finally on a real dig, Ally gets to try out her theories about dinosaur evolution and extinction with Brown himself. But just when it seems she is getting closer to her own time, Ally finds herself once again hurtled back millions of years and surrounded by the jungle-like flora of the Cretaceous period.

Ally is spellbound as a Pteranadon flies overhead and she watches an ostrich-like Ornithomimus devouring an egg in an enormous nest. But she is apparently not an unnoticed observer. When the creature spots her and moves to attack, Ally realizes that her adventure has become very real. Suddenly, a giant foot slams to the ground and the mammoth Tyrannosaurus Rex appears in the clearing, squaring off against the Ornithomimus to protect its eggs. In the midst of the battle, Ally is thrust literally nose-to-nose with one of the most fearsome creatures of all time - the awesome, and very much alive, Tyrannosaurus Rex!