Valerie Carlton was a journalist who accompanied Edward Perkins on his expedition into the Amazon rainforest to find out what happened to his great-grandfather's expedition.
While on the plane, she asked the Fourth Doctor about UNIT and alien invasions. When the plane crashed, she and the Doctor were captured by a tribe of natives and taken to their camp. When they were taken to their leader, they found out it was Edward Perkins great-grandfather Cornelius. When they asked asked the professor what year it was, he said 1873, and when he asked them what year they thought it was, she responded it was 1977. Intrigued by what sounded like a spaceship in the professor's diary, the Doctor asked Cornelius to take him to it. When they reached the spaceship, they found a skeleton with sharp teeth. When they decided to enter, the professor stayed outside, while Valerie and the Doctor entered. They found the ship had been stripped of its controls. When the spaceship started to topple over the cliff it was on, the Doctor managed to use the gravity inversion drive to fly the ship back onto the cliff.
When they found the lost city of the Maygor tribe, they were captured by the Maygor and taken to their "God" Godrin. Godrin had captured Edward and Leela and questioned them. He explained that he was the last of the Luron, a race of yellow skinned aliens with sharp teeth. He then said that his race accidentally destroyed their sun, so the last survivors went to other planets and stop them from the same fate. His ship was struck by a meteorite storm, and he crash landed on Earth, and his co-pilot was killed. The Maygor found him and thought him to be one of their gods. He then said that they were in a time bubble, and that it slowed down time.
After Godrin explained himself, it was revealed the professor was actually working for Godrin, who had promised to return him to his own time and be given some of the Maygor's gold. When the professor attempted to leave Godrin killed him. When Godrin asked to go to London, the Doctor accepted and repaired the plane with the gravity inversion drive and flew to London. When they called into air traffic control at an airport, they discovered, while in the time bubble, two years had past and their expedition was thought to be lost. When they got off the plane, Godrin betrayed them and revealed he was not the last Luron, and that the Luron mothership was orbiting Jupiter. He then knocked them out with a sonic device. When Valerie recovered, she woke the Doctor up and they set out after Godrin, leaving Edward and Leela behind.
The Doctor guessed that Godrin would make to a broadcasting station. Godrin did, and contacted the mother ship and told them to come into Earth orbit. After that he left. Valerie and the Doctor then went to UNIT HQ, and while there, General Hemmings took Valrie's camera to prevent her from taking any photos. Watching the television, Valerie saw a plane heading towards the mothership, and remembered it as the plane they left at the airport, and the Doctor guessed it was Godrin heading towards the mothership, and with Edward and Leelhttp://tardis.wikia.com/wiki/Valerie_Carlton?action=edit#a on board.
When Overlord Saldor announced that they would allow humans to come aboard their mothership, Valerie went with the party.
When the Luron plan was finally defeated, Overlord Saldor invited Edward and Valerie to come with the Lurons to a new planet. They both accepted. (AUDIO: The Valley of Death)