Today is like any other day in Grover Cleveland High's science lab - any day in the Jurassic Era, that is! Doc, the school genius, has rigged up a tight little time machine masquerading as an exercise bike, all fine and good until pretty-girl princess Heather cops a ride and drags herself, Doc and Lindsay Goldman - a.k.a. teen superhero GoGirl! - back several million years to the dinosaur-infested jungles of the long-gone past. As if being late for cheerleading practice isn't enough of an annoyance, try ditching a hungry T-Rex! And where did those alien spaceships come from?!