Learning that Donna and her fiancé Lance work for a locksmith company secretly owned by the Torchwood Institute, the Doctor asks Lance to take them there. Underneath the building, the Doctor finds a long tunnel under the Thames Barrier, and a secret laboratory producing huon particles, along with a pit that leads to the centre of the Earth. Their presence brings forth the spider-like Empress of the Racnoss. The Empress, who had been hiding in hibernation at the edge of the universe, awoke and used the Torchwood company to gain the equipment to make huon particles. Lance reveals he has been working for the Empress the whole time and purposely fed huon particles to Donna (by adding them to her coffee) to help free the Empress' children. Donna and the Doctor escape, and the Empress decides to use Lance as a substitute, force-feeding him huon particles and then throwing him into the pit, where he is eaten by the Racnoss children.