Far north of the Arctic Circle, a nuclear bomb test, dubbed "Operation Experiment", is conducted. Prophetically, right after the blast, physicist Thomas Nesbitt muses "What the cumulative effects of all these atomic explosions and tests will be, only time will tell". The explosion awakens a long carnivorous dinosaur known as a Rhedosaurus, thawing it out of the ice where it had been held in suspended animation for millions of years. Nesbitt is the only surviving witness to the beast's awakening and later is dismissed out-of-hand as being delirious at the time of his sighting. Despite the skepticism, he persists, knowing what he saw.