A geneticist, Dr Martin Nodel, is a researcher looking into introns, mysterious sections of DNA that he believes hold the secret to future evolution. He develops a formula that he believes will activate them, and tests it on himself.

After developing the liquid that acts on the intron (genetic material in DNA that acts as spacers and does not code for protein) he tests it on fish, and found that the liquid transforms the fish to amphibia. Then he tests it on himself, and begins experiencing strange symptoms, including a sort of map that grows on his back and a pattern that grows on his hand.

Shortly after he begins looking for students that are suitable candidates. They have to have a high IQ, never had surgery, and are free from imperfections such as tattoos or glasses. They also have to be in a certain age, weight, and height range.

After finding the needed candidates, he reveals the map. The area is discovered to be a hidden military area not on any normal map and, along with Nodel's son and his girlfriend, the group travels to the area.

Inside that area is a spaceship-type device with symbols that match the ones on the Doctor's hands. It activates, and a message from an apparent alien race is played back. The Doctor and the students decide to enter the ship on a journey to the home planet. Despite his son and son's girlfriend not qualifying, the Doctor says that they'd need someone like the two of them.

The ship takes off, and the episode ends.

Another episode released in season 4, "The Origin of Species", continues the story.

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