A journey back to the Jurassic period adorned with a plot to discover uranium- that is as contrived and unreasoned as Mr. del Rey's phantasy on Atlantis. In the future the U.S. has developed Time Slips that make excursions to the past. Young Chuck, an excursion guide, gets a mean party to handle, headed by Marsten. With no shooting of dinosaurs allowed, there's a mutiny when Marsten carelessly breaks their protective ""force field"" and decides to use his gun (why he had it along in the first place is never clear). Then Chuck finds two lost geologists who were hunting for the uranium Marsten himself is after, and the plot's uncovered. Far fetched.