Back at the command centre, the Doctor realises that the sea creatures are sensitive to high-pitched sounds, and he rigs up the centre's equipment to loop and amplify a recording of Victoria's screams into the pipes which lead to the central rig. The creatures invading the command centre through the impeller are also destroyed this way, using hand-held speakers. Through the video link, it is clear the foam has dissipated and all of the humans have returned to normal, including Robson and Mrs. Harris.