Thous was King of Atlantis at the time that Professor Zaroff discovered the lost city. He believed Zaroff's promise that he would raise the city above the sea, but eventually listened to the Second Doctor's warnings.
The Second Doctor and Ramo tried to convince Thous that Zaroff's plans were dangerous, but he turned them over to Zaroff. He later noticed the madness in Zaroff's eyes and tried to stop him, but Zaroff shot him. When the lower levels of Atlantis were flooded, Sean and Jacko helped the wounded Thous to the surface. Thous wanted to dedicate a stone to the Doctor, but Damon convinced him that they should build a new Atlantis, but this time without gods and fish people. (TV: The Underwater Menace)