Rose relates the story of how after travelling with the Doctor, she died.
The TARDIS arrives in modern-day London and Rose and the Doctor go to the Tyler estate. Jackie is glad to see her daughter and even gives the Doctor a kiss and hug. She then informs Rose that her granddad Prentiss is coming to visit. Rose is surprised, and tells the Doctor that Prentiss died 10 years ago. She figures that Jackie has lost it and reminds her mother that he died. Jackie agrees, and then turns to watch as a ghostly figure steps into the kitchen and stands next to Jackie. Jackie introduces Prentiss to her granddaughter.
Rose and the Doctor run outside and see ghosts appearing everywhere. One walks through the Doctor. Jackie explains that the mid-day shift will end in a few minutes and the ghosts will fade away. The Doctor is surprised to see that no one is running or screaming. As they watch, they are unaware that a scientist at the Torchwood Institute is shutting down a power system. The ghosts disappear right on cue. At Torchwood, the supervisor, Yvonne Hartman, informs everyone that they have measured the ghost energy and asks for a round of applause.
The Doctor and Rose watch as newscasters across the world casually discuss the existence of the ghosts, and their general acceptance by the populace. Jackie confirms that the ghosts first started appearing two months ago. People panicked at first, but soon accepted that they were lucky to be reunited with their loved ones. The Doctor realizes that people are wishing the ghosts into existence, and they're using that energy to pull themselves in. Jackie points out that they look human, but the Doctor warns that it's not conclusive.
At Torchwood, Yvonne checks with her underlings, Adeola and Dr. Rajesh Singh, who confirm that there is no power loss. Singh informs her that R&D created a new spectrometer that detects heat sources, but it doesn't register anything from the sphere. Singh observes the sphere and admits that it tends to get into one's head. Once Singh signs off, he climbs up to the sphere and tries to place his hand on it, but is repelled.
In the Torchwood office, Adeola sends a "bored" text message to her coworker, Gareth, and invites him to a quick snogging session. Gareth and Adeola soon slip away to an out-of-bounds area under construction, and the workers are allocated somewhere else. Adeola isn't sure but Gareth goes in without her. She tells him that she's going back and she'll see him tonight. Gareth doesn't respond and Adeola goes in through the plastic sheets to find him. When Gareth doesn't respond, Adeola gets nervous but keeps looking for him and finds what appears to be a worker. She pulls aside the sheet and finds herself face-to-face with a Cyberman.
The Doctor and Rose return to the TARDIS and the Doctor gets a piece of equipment to track the ghosts. When the next shift starts, he tries to triangulate their point of origin. When Jackie wonders why he has to reduce it down to science, the Doctor warns that it's horrific. He runs back into the TARDIS and tells Rose to monitor the signal.
At Torchwood, Yvonne tells everyone to prepare for the next shift. Gareth and Adeola appear, and emotionlessly take their positions. The earpieces glow with a blue light as they monitor the systems.
The Doctor activates his triangulation device while Jackie watches Rose at the TARDIS controls and wonders what she'll do when Jackie is dead and she has nothing else to come back for. Jackie worries that Rose is becoming less and less human.
At Torchwood, the technicians activate the system and they go into ghost shift.
The Doctor watches as one of the ghosts appears within his triangulation device. He activates some controls and at Torchwood, an alert goes off, interfering with the ghost field. Gareth confirms that the source is close, within the system. Meanwhile, the Doctor's ghost lashes out at the triangulation system as it tries to escape. It finally fades away as at Torchwood, Yvonne shuts down the system. Yvonne pinpoints the disruption to the Powell Estate. They patch into the CCTV system and spot the TARDIS, and realize the Doctor is involved.
The Doctor enters the TARDIS and sets course for the disruption. Yvonne watches it and realizes that the Doctor is coming. She notifies Singh, who looks up at the sphere in triumph. Meanwhile, Rose reminds the Doctor that Jackie is still on board.
Torchwood soldiers greet the TARDIS when it arrives in a storeroom. The Doctor tells Rose to stay with Jackie while he goes out and confronts the soldiers. Yvonne arrives and is pleased to meet him, and leads everyone in a round of applause. He's surprised to hear that they've heard of him, and that they appreciate his saving them. Yvonne asks to see his companion, well aware that he travels with a female, and the Doctor ushers Jackie out and introduces her as Rose. Yvonne welcomes the Doctor to Torchwood and shows him to a large storage room filled with alien ships and technology. She explains that they’ve been stripping aliens for alien technology, and that they plan to use it to recreate the British Empire. The Doctor warns that they're not ready for the technology, but Yvonne is unimpressed. He notices a pair of magna-clamps, and Yvonne explains that they can use it to lift heavy weights.
The Doctor asks about the ghosts, and Yvonne says that they are a side effect. As they talk, the Doctor notices that they're taking the TARDIS away, and warns they'll never get in. He glances briefly at Rose at the door, and she goes to get his psychic paper.
In the control room, Adeola invites a co-worker, Matt, to come with her and see something good. She walks away and after a moment, Matt goes after her.
As they tour the facility, Yvonne explains that the Torchwood was created in 1879 after Queen Victoria encountered the Doctor fighting werewolves. He's considered an alien enemy but will be kept comfortably. She shows them to the room with the sphere, and Yvonne explains that it gives off a psychic repulsion field. Singh explains that according to their sensors, it doesn't exist. The Doctor explains that it's a void ship, capable of traveling in the void between parallel universes. When Yvonne wonders how they can use it, the Doctor says they have to send it back to Hell. Yvonne explains that the sphere appeared on Earth and the ghosts followed in its wake, and he tells her to take him to the control room to see the readings.
Matt follows Adeola into the construction area and she tells him to continue on without her. He sees a glowing red light and follows it, and seconds later Adeola leaves as screams ring out.
Rose emerges from the TARDIS and grabs a lab coat. Donning it, she walks through the complex posing as a scientist.
Adeola returns to the control room as Yvonne shows the Doctor the wall that the sphere came through. She explains that when they fire particle accelerators at the wall, the ghosts appear. They built Torchwood Tower around the breach. Jackie looks out and realizes that they're at Canary Wharf. Yvonne insists they can massive the energy to become independent from oil, and says they can see when they bombard the wall again in two minutes. The Doctor tells her not to, but Yvonne refuses. In response, the Doctor explains that when the void ship came through, it created splinters and the ghosts are coming through, enhanced by human wishing for them to be there. If too many come through, it will shatter the world. Yvonne says they'll be more careful, but the Doctor warns that it won't be enough. When it's clear she won't listen to him, the Doctor pulls up a chair and prepares to watch the destruction. Yvonne finally orders the technicians to stop the shift and agrees to find as much intelligence as possible. She promises that they programme will recommence once the Doctor explains, and he agrees to help. Meanwhile, Adeola, Gareth, and Matt, who has returned and is wearing the same altered earpiece as the other two, watch and access the particle accelerator.
Rose spots a scientist running through the halls and goes after him. She follows him to the void ship chamber. Singh spots her and demands to know who she is, and she shows him the psychic paper while claiming to be from Personnel. Singh explains that he has basic psychic training and calls security. He tells one of the technicians to check the locks, and Rose realizes it's the man she followed in... Mickey, working undercover.
Singh calls Yvonne and tells her about Rose. The Doctor denies knowing her until Yvonne says she's gong to have her shot. Yvonne notices that the ghost shift programme is running and orders Adeola and the others away, but they ignore her and finish the process. The Doctor realizes that Adeola is being controlled.
In the void ship chamber, the vessel activates.
The Doctor uses his sonic screwdriver on Adeola's earpiece. She and the others collapse, dead, and the Doctor explains that someone already killed them. When Yvonne pulls one out, she realizes that it is connected directly to their brain. The Doctor realizes that there's a transmitter nearby still overriding the system.
Singh calls Yvonne and informs her that the void ship now exists. The doors seal on them because of automatic quarantine. Meanwhile, Mickey tells Rose that he beat them before and can defeat them again, and she realizes they're up against someone they've met before.
The Doctor leaves Jackie in the control center and takes Yvonne and two soldiers with him to track the transmitter. They go to the construction area and the Doctor tells her to go back. She refuses and they advance, and the Doctor explains that their world is colliding with another. Cybermen emerge through the sheets and the Doctor explains that they're the advance guards. The soldiers' bullets have no effect.
Mickey explains that the Cybermen on the parallel world all vanished when they were on the verge of defeat. They determined a way to get Mickey back to his own world, and he figures that the Cybermen have their Cyber Leader in the void ship.
The Cybermen advance guard enters the control center and the Doctor tells everyone not to resist. The Cyber Leader increases the ghost shift to 100% and ghosts appear across the world. Ghosts march through the void wall, while Singh tries to contact anyone for help. The void ship opens and something emerges.
The Doctor explains that all of the ghosts are Cybermen... millions of them appearing across the world. The "ghosts" fully manifest as Cybermen and take over homes, government buildings, and news stations. The Doctor warns that it's too late, and the Cybermen have already won. They watch on the monitor as the void ship activates.
In the void ship chamber, Mickey gets out a hidden weapon designed to defeat Cybermen.
The Doctor asks the Cybermen how they built the void ship, which is beyond their technology. The Cyber Leader explains that the void ship is not theirs. It broke down the barrier between worlds and they used it to mount their invasion, but its origin is unknown.
The void ship's occupants emerge, and Mickey, Rose, and Singh look on in horror as three Daleks emerge.