Sister Helena was one of the nuns at St Agnes Abbey. She and the other nuns, while being mentally influenced, looked after the Gorgon. She also went to Lavender Lawns looking for the Talisman.
She then went to Sarah Jane Smith's house and tried to get hold of Luke and Clyde but failed. She later captured Luke and locked him up. She and the other nuns were freed from the Gorgon's mental influence when the Gorgon was defeated. Helena, after being freed of the Gorgons control, suffered temporary amnesia and gasped in horror as the other Gorgons started to come through a portal, but the Gorgons were stopped when Maria Jackson disconnected the Talisman. The gang rushed off to save Maria's father, who had been turned to stone, leaving the incredibly confused nuns with a very ugly garden ornament and in need of a new Abbess. (TV: Eye of the Gorgon)