Now that she's traveled with the Doctor for so long, Romana is upset to learn the Timelords have recalled her back to Gallifrey. She sulks in her room till the Doctor comes to see her. She wants to rebel against the Timelords and refers to the Doctor even doing so at one point. He reminds her on that occasion, he lost. Of course he's referring to events that led up to a forced regeneration and being marooned on Earth. As they are discussing this in her room, K-9 is monitoring the Tardis flight.
As K-9 is monitoring the Tardis, they are drawn into a CVE (Charged Vacuum Emboitment), a space anomaly that takes them out of normal space and into E-Space. The Tardis lands on the planet Alzarius, but it's supposed to be Gallifrey. As this is E-Space, all co-ordinates are negative, but the Tardis is having trouble comprehending that. As the Doctor and Romana are talking, a young boy wanders into the Tardis. it's Adric. He's just run away from a group of kids led by his brother after he was caught stealing fruit. They are kids who have rebelled from life about the Starliner, a ship marooned on the planet.
The planet has fallen into mistfall, a time when strange creatures rise from the Marsh. Of course the Doctor decides to investigate. When he comes upon a Starliner, he sneaks in but is followed by one of the creatures. He's soon discovered by the inhabitants of the ship who also find the creature. He urges them not to over-react to the creature and he tries to calm it down. The ship staff want none of that and knock out the Doctor and take the creature for further study.
While the Doctor is investigating the ship, Adric has left the Tardis but Romana gives him a homing beacon to find it again. Back with his brother's little gang, he tells them about the Tardis. Despite Adric's protests they force him to take them to the Tardis. Romana is clever though, and disarms the group, with Adric's help. After a quick flight in the Tardis, Romana leaves to investigate a cave, but she's bitten by a fruit spider and her mind is suddenly like that of the Marshmen. As Marshmen suddenly arrive to attack, K-9 tries to fight them off, but is beheaded by one of the creatures. Scared, the group in the Tardis begin to press various buttons and the Tardis dematerializes.
The Tardis re-materializes on the Starliner, and Romana and the Marshmen make their way for it. They break into the ship and cause havoc while the Doctor tries to find a cure for Romana and do more investigative work into figuring out what the Marshmen are. A cure is found, and the Doctor discovers the residents of the Starliner are actually descendants of the Marshmen. Pure oxygen drives them away, but they are adapting quickly. Pumping the ship full of Oxygen drives them from the ship and back to the swamps. However, Adric's brother dies in the process. Grieved, he sneaks into the Tardis as the Doctor is explaining to the Deciders how to operate their ship, something no one has ever figured out how to do, as the ship has been there for 40,000 generations.
PLANET OF ORIGIN: Alzarius, unknown time.
REASON FOR JOINING: After the death of his brother and bored with the Starliner, Adric stows away in the Tardis.
NEXT: The Gateway