Maria's dad Alan (Joseph Millson) has been turned to stone. The alien talisman is now in the possession of the Gorgon and her evil nuns, and they are preparing to open the portal to their world. Can Sarah Jane (Elisabeth Sladen) and her young friends free Alan from his stony state, prevent the nuns from unleashing more deadly aliens on the Earth, and avoid the Gorgon's petrifying gaze?