investigating whether Pierre Dudoin's company, ITI, has been in contact with aliens. Together they break into the ITI headquarters and find an alien called Sa'Motta tending to Dave. Sa'Motta explains that he came to Earth in a failed invasion spearhead four years ago and has been stranded which prevents him from stopping their leader, Fray'kon, from reporting that Earth should be invaded by the Kulans. Fray'kon has been helping Dubion's ship near completion to rejoin the invasion fleet. The other Kulans in the spearhead just want to return home and have been helping Tyler's ship. However Kulan ships need telepathy to work, so research has been done to produce a hybrid who can work the ship. The dead man had been giving the genes necessary to Tyler, but injected them into Dave to preserve them. However, the genes injected into Dave are slowly killing him. As guards recapture Dave, Fisher's boss orders a squad to capture Fitz and Sa'Motta. Meanwhile, the Doctor and Anji go to Tyler's base and save his life after a Kulan computer virus planted by Dudoin traps Tyler in a room with a fire. The Doctor puts the virus on a DVD for study. The Doctor offers to help stop Dudoin and Fray'kon's plan, but Tyler's ship is destroyed by an after-effect of the virus. Tyler turns to his former friend and Dudoin's ex-wife Christine Holland to help with adapting the Kulan technology for humans, but before he can contact her, Dudoin kidnaps his daughter Pippa to force her to come to Brussels to help Dave. She does so, but Dudoin reveals he plans to launch the rocket without testing it. Christine sees Fray'kon tamper with the controls, but Dudoin refuses to listen. Fitz and Sa'Motta attempt to go to London, but realise they are followed by CIA agents. Fitz is captured and taken to the CIA's agent known as Control, but Sa'Motta escapes, and makes the way to the CIA base where Fitz is being held. Control puts a tracer on Fitz and allows Sa'Motta to rescue him to lead the CIA to the other Kulan. While escaping, Fitz realises that his memories of the destruction of Gallifrey are getting blurred and hazy. In space, the invasion fleet moves into its final formation, ready to invade on Fray'kon's command. Meanwhile, the Doctor rescues Christine's daughter and asks for Tyler's help in stopping Dudoin and Fray'kon