Sabetha was a young woman sent by her father, Arbitan, to find the keys to the Conscience of Marinus. She instead became enslaved in the city of Morphoton. After being freed, she accompanied the First Doctor and his companions in their search for the keys.
Sabetha and Susan were captured by Vasor, who stole the keys from them and abandoned them in ice caves. After they were rescued by Altos and Ian, they retrieved the keys from Vasor and obtained another from the ice cave.
As the Doctor and his companions sought the last key, Sabetha and Altos went ahead with the rest of the keys. They were captured by the Voord Yartek, who had killed Arbitan and took his place. Sabetha and Altos were romantically involved, a relationship which was exploited by the Yartek. After Yartek was defeated, Sabetha and Altos planned to return to Millennius. (TV: The Keys of Marinus)