Originally aired: Saturday May 19, 2007 on BBC-1 Writer: Chris Chibnall
Director: Graeme Harper
Show Stars: Freema Agyeman (Martha Jones (Season 3 - )), David Tennant (The 10th Doctor (Season 2 - ))
Recurring Role: Adjoa Andoh (Francine Jones)
Guest Stars: Rebecca Oldfield (Erina) , Gary Powell (Ashton) , Vinette Robinson (Lerner) , Matthew Chambers (Korwin) , William Ash (Riley) , Anthony Flanagan (Scannell) , Michelle Collins (McDonnall) , Elize Du Toit (Sinister Woman)
Production Code: NCFT087E
In the TARDIS, the Doctor adjusts Martha's mobile phone, enabling it to call anywhere in time and space - an ability he refers to as Universal Roaming. As she is about to telephone her mum, they materialise on a very hot spaceship (in answer to a distress signal), and the Doctor notes that the engines are not operating. They open the door to the next room and are pulled through by three members of the crew, who then slam the door shut. The captain, McDonnell, explains that the engines have cut out and left the ship on a crash course with a local star. A nearby monitor announces that the projected time until impact is 42 minutes. The Doctor suggests evacuating the crew on the TARDIS, but the ship has begun venting excess heat through the room it materialised in, rendering it unreachable.
The Doctor organises Martha and one of the crew to open a series of password-protected doors in order to access to the control room where the auxiliary engines can be activated. Meanwhile the rest move to the main engine room, to try to fix the systems. The Doctor finds that all the engine-related machinery has been destroyed, and comments that someone "knew what they were doing."
There is a call from Abi, a medic, to say that Korwin, McDonnell's husband, is having some sort of seizure. The Doctor tells everyone else to continue trying to save the ship and he runs to Abi to find the others have followed him. They go to find Korwin lying near a stasis chamber with his eyes closed, screaming in agony, crying "It's burning me!" before the Doctor sedates him. Upon sedation the Doctor instructs Abi to test Korwin to find out what is wrong with him then the Doctor and McDonnell return to the rest of the crew.
While updating the crew on Korwin's status, the crew hears Abi's screams for assistance as Korwin gets up and backs Abi against the wall, saying in a deep voice, "burn with me". As he opens his eyes, a blinding light comes out and Abi screams in terror.
While the Doctor runs to Abi's aid, Martha and Riley continue to open doors by answering pub quiz style questions set by the crew, years previously, after a night of drinking. The questions include a crew member's favourite colour, and the next in a series of what turn out to be happy prime numbers. To answer another question, Martha has to ring her mother to ask her to find out the answer to the question "Who had more pre-download number one hits, Elvis Presley or The Beatles?" and we find out that Martha's mum has her call tapped. Meanwhile, the Doctor finds the imprint of Abi and concludes that she was vaporized. He reasons that Korwin has been infected in some way by something, and can vaporize people somehow.
McDonnell is at first unwilling to believe that her husband could be responsible for sabotaging the ship and killing Abi, but then alerts the rest of the crew to avoid Korwin. Ashton, working on the engines, sends Erina a message asking for more tools. She mutes the sound and mutters under her breath about the injustice of being sent on every errand as she goes to the control cupboard. She sarcastically ends her spiel with "just kill me now." When Erina closes the door, she turns to find Korwin standing there. He then says "burn with me, burn with me" and backs Erina against the wall as with Abi, and vaporizes her. Then Korwin goes to find Ashton, saying "they are getting too far". He places his hands on Ashton's temples, who screams in pain, and becomes infected too. Ashton goes after Martha and Riley, who in terror lock themselves in an escape capsule.
Ashton tries to override the system and send Martha and Riley plummeting towards the sun, but Riley is trying equally hard inside the capsule to stop this from happening. Ashton finally just punches the system and this makes the capsule Martha and Riley are stuck in plummet towards the sun. The Doctor gets there at the last second and yells to Martha "I'll save you!" over and over again- but she can't hear him. The Doctor puts on a space suit and tells McDonnell he is planning to pull the capsule back to the ship by setting the magnetic pull off, a system that is outside the ship. They tell him it is hopeless but he does it anyway. He struggles to press the buttons on the side of the ship and when he finally manages it he yells "come on my son!" Climbing back into the ship, he looks at the sun and realises that "It's alive", repeating the phrase a number of times, before he too is infected by the same thing as Korwin. Martha and Riley come back to the ship grinning until they see the Doctor in agony. McDonnell arrives and the Doctor explains to her that because she illegally mined the sun for fuel, without checking for life signs, she has seriously injured the living being within the sun. He tells them that the sun is alive in him, and tells them how they can save/stop him. He has his eyes shut, like Korwin, and cries for Martha to stay with him, telling her that he is scared. He has to be put into a freezing machine, to get the sun out of him, and before he goes in he tries to tell Martha about the regeneration that may happen.
Martha starts the freezing process but it is interrupted by Korwin, who turns off the power to the stasis (freezing) chamber from a remote location (engineering). The Doctor then tells Martha that she must go to the front of the ship and jettison the fuel, which will return the living particles back to the sun. Martha runs to tell the rest of the crew to jettison the fuel while McDonnell encounters Korwin. McDonnell admits to Korwin that this was all her fault and lures him close to an airlock. She tells him that she loves him and then opens the airlock and the two of them float into space. Martha tells the rest of the crew to vent the fuel, which ends the crisis and ends the sun creature's control over the Doctor.
The Doctor and Martha head back to the entrance of the TARDIS, where Riley kisses Martha goodbye. Inside the TARDIS, the Doctor gives Martha her own key to the TARDIS. Martha calls her mother back, and we learn the woman tapping the phone works for Harold Saxon.