The team returns to Mexico City to take their injured colleague to a hospital. Still on his arm is a small piece of the blob, which is slowly digesting him. The surgeons carefully remove the creature, wrapping it up. They find that his arm is nothing more than a few moist scraps of flesh still connected to the underlying bones. After further experimenting on the creature, scientists discover that it is a unicellular bacterium that quickly grows when in the presence of radiation. A comet emitting radiation, that crosses Earth's path only once in every 850 years, is quickly approaching. At the comet's closest approach to Earth, the remaining piece of the blob removed during the surgery begins expanding to an enormous size and reproducing. Unfortunately, the removed sample of creature is stored in the home of expedition member Dr. John Fielding (John Merivale).