Rose narrates her life, and how she did nothing in the first 19 years of her life… and then died. She talks of how the Doctor showed her all of time and space, and how she promised she'd stay with him forever. She talks of the Army of the Ghost, Torchwood, and the War, and everything ended.
The TARDIS materializes and the Doctor and Rose come out to visit Jackie, drop off Rose's laundry, and give her a souvenir. Jackie says she has a surprise of her own: Rose's grandfather Prentis. Rose believes Jackie has lost it, since Prentis has been dead for 10 years. Right on time, a black featureless figure steps through the wall and Jackie says it's Prentis. The Doctor and Rose run outside and see more of the figures, and one of them passes through him without effect. Jackie describes that the ghosts appear and disappear in "shifts." The figures all disappear on cue as elsewhere, scientists in a Torchwood facility shut down a power source at the same moment.
A woman, Yvonne Hartman, congratulates the Torchwood team while the Doctor, Rose, and Jackie watch several television broadcasts about the ghosts whose existence has infiltrated human society across the world. Jackie reveals it started two months ago and that she can tell it's Prentis from his feel and his smell, and says that someone has to want it to sense who the ghost is. Rose can't sense anything, and the Doctor reveals that the "ghosts" are drawing on the psychic link to pull themselves into the real world. Rose notes they're human looking but the Doctor notes a footprint doesn't look like a foot.
Yvonne talks with one of her staff, Rajesh Singh, who is analyzing a sphere without luck. His equipment doesn't even show that it exists. He briefly considers touching it but then flinches away, nervous. Yvonne has two of her workers, Gareth and Adeola, send some info down to Rajesh to keep him occupied. The two of them flirt via e-mail and go out for a tryst, entering a part of the building under construction. Gareth walks through the sheets a few steps ahead of Adeola. When she tries to find him, she pulls aside the construction sheets and sees a figure on the other side. She asks the figure if he's seen Gareth, and it reveals itself as… a Cyberman.
The Doctor has returned to the TARDIS where he's rigged a backpack device to lock into some beacons which he places nearby to track the ghosts' energy signature. He, Rose, and Jackie enter the TARDIS with two minutes to spare.
Yvonne prepares for the next shift as Adeola and Gareth return… acting somewhat mechanically. As the scientists power up the shift, the emitters on the two workers' ears start to flicker.
As the Doctor works on the beacons, Jackie notes that Rose is becoming more like the Doctor, and wonders if her daughter will have any reason to come home once she dies, and she'll be something other than Rose Tyler, something… inhuman.
The ghost shift occurs and one appears within the beacons, trapped. An alarm goes off at Torchwood and Yvonne orders a shutdown while the Doctor tries to get more info. The captured "ghost" disappears as Torchwood shuts down the power. Then Yvonne and her assistant track the disturbance to Jackie's apartment flat and patch into the CCTV network… where they spot the TARDIS just after the Doctor enters it. Yvonne recognizes it for what it is as it dematerializes. Yvonne runs out of the room to notify her superiors while Rajesh considers the sphere. The Doctor and Rose home in on the signal and it takes a minute for him to realize that Jackie is still on board.
The TARDIS materializes in a basement facility where armed Torchwood soldiers surround it. The Doctor steps out alone and Yvonne arrives… to give him a round of applause. She thanks him for making sure Earth has survived and wonders what companion is with him. He ends up pulling out Jackie and hastily explains that she was aged by exposure to the Time Vortex. Rose observes on the TARDIS scanner as Yvonne leads the Doctor and Jackie out.
Yvonne gives them a tour of the Torchwood facility, showing them the alien technology that they've salvaged and used ever since. The Doctor is concerned that they have access to advanced technology but Yvonne dismisses his concerns. She also declines to answer his question about the ghosts and Jackie notices the TARDIS is being taken away. The Doctor is confident she can't get in and secretly signals Rose to stay inside. She gets the Doctor's jacket and takes out the psychic paper.
In the control room, Adeola and Gareth persuade another co-worker, Matt, to come look at something. Meanwhile, Yvonne explains how they know about the Doctor from his encounter with Queen Victoria (in "Tooth and Claw"), and he is now their (rather comfortably kept) prisoner. She takes him to see the sphere and Rajesh explains how it gives off nothing and shows up on no sensors. The Doctor identifies it as a void ship, which is technically impossible. It's a vessel designed to exist outside of time and space and capable of traveling between dimensions. They figure there's something inside but the Doctor tells them they should send it back. Yvonne explains it came into their reality and the ghosts followed, and she takes the Doctor to see.
Adeola and Gareth take Matt into the construction area where the sound of drills ring out as Matt screams in agony.
Rose slips out of the TARDIS and quickly disguises herself as a scientist. She follows one of the other scientists into the facility, while Yvonne shows the Doctor where the void ship appeared, and they built a skyscraper atop the site to get to it and cover up its existence. Yvonne explains they have been making the breech larger to tap into its energy to become independent on oil. The Doctor tells her to cancel the next ghost shift and demonstrates with the sonic screwdriver how the dimensions are splintering and the ghosts are coming in through the fault lines. Too many ghosts come through, and the breech will shatter. Yvonne refuses to back down and the Doctor gives up, settling down to watch the fireworks. At the last second Yvonne calls off the next shift and agrees to conduct further investigation.
Matt is back at his station along with Adeola and Gareth, and they are using the computers to access the power system.
Rose makes her way through the facility to where the void ship is. She tries to bluff her way path Rajesh with the psychic paper but all Torchwood employees have low-level psychic abilities and he isn't fooled by it. Another scientist in the room steps forward--it's Mickey. However, Rajesh knows him as "Samuel" and tells him to capture Rose. Mickey signals to Rose not to give him away.
The Doctor concludes that the ghosts built the sphere but he's interrupted when Yvonne gets word that Rose is present. The Doctor tries to bluff not knowing her but Yvonne quickly catches on. However, they're interrupted when the ghost shift starts to power up again on remote. The Doctor spots Adeola and realizes she's activating the systems to initiate a ghost shift.
Rajesh tries to contact Yvonne as the void ship starts to move and tremors shake the building. The Doctor recognizes the earpiece Adeola is wearing and uses his sonic screwdriver on it, shorting it out on her, Matt, and Gareth, and killing them. Yvonne pulls it out and reveals it was tied directly into Adeola's brain. He tries to locate the remote signal while Rajesh calls for help as the void ship starts to take on mass and "reality." Mickey and Rose look on as he reassures her they've beaten "them" before.
The Doctor, Yvonne, and Torchwood soldiers investigate the construction area while Jackie stares at the breech wall. The Doctor recognizes what world the ghosts came from as the Cybermen advance on them. The soldiers open fire without any result, while Mickey explains that he came back from the parallel world after the Cybermen disappeared from there. The Cybermen take the Doctor and the others prisoner and rev the power up to 100%. The "ghosts" materializes all over the world in increased numbers and the breech opens as more Cybermen march through.
In the lab, the void ship starts to open as the Doctor explains to Jackie that the ghosts are Cybermen and now millions of them have been unleashed. The "ghosts" everywhere manifest into Cybermen and the people run in panic. The Doctor says it's too late and the Cybermen have completed their invasion.
The void ship starts to open and Mickey pulls out a hidden high-energy guns. He goes to confront them while the Cybermen reveal that the sphere isn't theirs and they only followed it. Rose, Mickey, and Rajesh stare in horror as… Daleks emerge from the void ship.