The TARDIS arrives in the far future on Satellite Five, an orbital broadcasting platform orbiting Earth in the year 200,000, so that the Doctor (Christopher Eccleston) can show Rose (Billie Piper) and his new assistant Adam (Bruno Langley) the wonders of the planet at the height of the fourth Earth Empire. The Doctor, however, realises that something is terribly wrong with the technology of this time period, with which he is very familiar, and so he sets out to question the first two people he finds, two journalists named Cathica (Christine Adams) and Suki (Anna Maxwell-Martin). Using his psychic paper as his credentials, the Doctor is mistaken as a management employee testing the two, who tell him that Satellite Five controls all of the news broadcasts to the human race. The two take Adam, Rose and the Doctor to a network link room, a spartan space where six journalists sit in a circle while the seventh accesses a compressed data stream beamed directly into a linking apparatus installed upon their head -- in essence, correlating and distributing all of the data known to mankind. However, a sudden spike breaks their link while Suki receives word that she's been promoted to "floor 500," the top level of Satellite Five, considered a great honor.

Suki goes to Floor 500, where she runs into trouble when she discovers the level is nearly frozen and the only sign of life is a strange man called the Editor (Simon Pegg), who runs the satellite along with a pack of corpses reanimated through manipulation of their implanted data chips. The Editor tells Suki she was promoted because he's discovered she really isn't a journalist; she's a freedom fighter from Earth attempting to get to the bottom of Satellite Five's true nature. However, before Suki is able to kill him with a weapon she's smuggled aboard, she is confronted by the Editor's 'boss,' as she looks up into the rafters and screams...

Adam feigns exhaustion from being overwhelmed by the culture shock, while the Doctor and Rose set off with Cathica to do some investigating. Adam discovers that he can't access the computers here - after attempting to gain some information about this future and transmit it back in time to his parents' answering machine while using Rose's modified mobile phone - and goes to the medical floor. There, a nurse (Tamsin Greig) tells him about the data implant that he can have put in. Adam decides to get the implant, so he can access the information and again call his home. Meanwhile, the Doctor and Rose access Floor 500 as a frightened Cathica follows them. The Doctor and Rose are captured by the Editor and his undead henchmen, which now includes a brain-dead Suki, and are confronted with the truth: Satellite Five is the home of the Mighty Jagrafess of the Holy Hadrojassic Maxarodenfoe, a massive alien creature that sits in the space above the Editor's control room, guiding Earth along its predetermined path through the manipulation of broadcast media. The Editor demands to know who the Doctor and Rose are, as they don't show up on any census reports... but suddenly the Editor becomes aware that the Doctor is a Time Lord and that they travel in a TARDIS, and shows them how he knows: Adam is now in the data link chair, and everything within his mind has been transferred into the network, including the Doctor's identity.

Cathica discovers a forgotten data link area nearly frozen over outside the Editor's control room, and gets into the chair. As the Doctor and Rose are about to be devoured by the Jagrafess, Cathica uses her link to reverse the temperature controls, forcing the heat to spike in the control room and injuring the enormous creature. The Editor attempts to escape, but one of his undead lackeys traps him, while the Doctor, Rose and Cathica barely escape Floor 500 before the Jagrafess is pulverized. The TARDIS crew departs Satellite Five, leaving the cleanup in Cathica's capable hands. The TARDIS later materialises in Adam's parents' home, where the Doctor uses his sonic screwdriver to destroy the answering machine, and the data about the future that Adam left there. Adam asks the Doctor to take him back into the TARDIS, as he's got the data terminal in his forehead and can't stay like this forever, but the Doctor leaves him that way, noting that Adam will now have to stay silent in order to not attract any attention to himself... and that he only travels with the best, and Adam isn't it. As the TARDIS departs, Adam's mum comes home, but soon realizes something strange has happened to her son...