Cleo Proctor is officially over it. Her life is a mess. She wants the Doctor to take her away from all this, but they're not returning her calls. Then Cleo discovers reports of mutant rats in London Docklands and things get interesting.
Attacked by giant rats, Cleo's expecting the Doctor to turn up - but instead she encounters a different enigmatic alien. Apex Costa explains he needs Cleo's help. Abby and Shawna investigate a mysterious organization called Torchwood.
To save Apex's life, Cleo must venture deep into the alien underground beneath London. But dark secrets are lurking down there. Meanwhile Abby and Shawna are hunted in a library by a shape-shifting monster.
Cleo learns that Apex isn't all he claims to be. And he's in debt to the powerful Honour Bray. Has Apex been using Cleo all this time? Meanwhile Abby and Shawna follow the trail of a thief who's been stealing dangerous alien artifacts.
Abby and Shawna go to meet Rani Chandra at Bannerman Road, but they aren't expecting the house to be booby-trapped. Meanwhile Cleo is taken hostage by Honour Bray. She learns the truth of her twisted plan and meets the giant metal "Cobot".
Cleo is in a race against time to defeat Honour and save the alien refugees of the London Underground. She needs all the help she can get - Abby, Shawna and the Doctor would be useful too. But which side is Apex on?