Scotland in 1965. A bus full of children is driving across the countryside. It stops in the middle of the road and the children, confused and scared, get out. A bright light appears ahead of them and all but one of them walk into the light. The last boy looks back hesitantly as the others continue.
Cardiff in the present day. Gwen is taking money out of an ATM and notices several parents trying to talk to their children, who appear to be in a trance. Across the country, other parents are discovering that their children have become entranced. Rhys is caught in traffic when children come to a dead halt on a crosswalk. All of the children suddenly snap out of their trance at the same time and go back to what they were doing minutes before with no memory of what happened.
Gwen goes to the new Torchwood Hub and wonders what Jack and Ianto are up to. She gets no answer and goes to her workstation.
At St. Helen's Hospital, Dr. Rupesh Patanjali is trying to revive a patient, Mr. Williams, without success. He calls the time of death and goes out to see Jack and Ianto. They claim to be the dead man's neighbor and ask to see the body. Once they're alone with it, they get out a laser saw and cut open the dead man's chest. Jack starts to pull out a large parasitical creature as the doctor comes back and stares in shock. Jack and Ianto pack away the parasite, seal the body back up, and leave. The doctor follows them and demands answers, and wonders if they're Torchwood. Jack denies it but the doctor says that bodies have gone missing. Jack asks for more detail and Dr. Patanjali explains that five bodies of different nationalities have disappeared from the morgue in the last two months. Jack and Ianto consider the matter, figure the NHS is the best place to start.
John Frobisher arrives at the Home Office and meets with Colonel Oduya. Lois Habiba comes in just behind him and is greeted by Bridget Spears on her first day of work. Meanwhile, Oduya warns Frobisher that there's something wrong with the children.
Jack and Ianto return to the Hub and Jack asks Gwen to do a check on St. Helen's. Gwen tells him to do it himself and reports there were seventeen road traffic accidents at exactly the same moment, and each of them involved children. In each case, the children froze. Ianto confirms that similar incidents occurred across the world at the exact same moment.
Oduya gives Frobisher the same report and concludes that every single child in the world stopped. The UN has placed UNIT on yellow alert. Lois comes in to deliver coffee and Frobisher and Oduya switch to innocuous conversation. Lois introduces herself and Frobisher dismisses her. She goes out and asks Bridget what uniform Oduya is wearing, but Bridget tells her to get to work. Meanwhile, Oduya notes that they'll crush any news stories and that his people are on to Torchwood.
At the Hub, Jack ends up talking to a sergeant at UNIT because Martha Jones is on holiday. So far all tests have proven negative. Ianto informs Jack that Rupesh is outside and they explain to Gwen who is. Jack admits they need a doctor and Gwen realizes they suckered him in the same way they did to her. She goes out to bring him in and Jack complains that Gwen called them a couple. Ianto is upset at her comment.
Gwen goes outside and talks to Rupesh. They go to a cafe and Gwen notices that three of the missing bodies were Chinese, a statistical anomaly. They talk about how Rupesh came down from Chesterfield eighteen months ago and Gwen explains how much Torchwood pays. When he asks what they do, Rupesh admits that it sounds exciting and glamorous, and notes that they've all seen alien life in the past two years. He talks about how suicide rates have doubled since aliens first appearing. His first case was a suicide and the victim, a religious woman, had written letters saying that science had won and her place in the world was tiny. Gwen admits she once had the same feelings. However, she notices a child going into a trance nearby and runs over while calling Jack.
Across the world, all the other children go into a trance and then start giving off a high-pitched screaming noise. Jack and Ianto run up and take recordings, and the children suddenly say "We" in chorus. They then speak further, saying "We are coming" repeatedly.
Frobisher gets a report and tells Bridget to bring in a child, any child. At a sanitarium, one older man says the same thing in chorus with the children. All the children then go back to normal at the same time with no memory of what happened. At the sanitarium, the man also collapses and tells the staff that "they" have found him.
Jack, Ianto, and Gwen head back to the Hub and Rupesh follows them. Jack points out the hospital will need his help and Rupesh reluctantly abandons them.
Frobisher's office is overwhelmed with calls and he finally tells his staff to cut them off. Bridget gives Lois her password to set up an auto-response. Mr. Dekker arrives and demands to see Frobisher. He says "456" and admits that he warned Frobisher.
Jack tries to call Frobisher and gets Lois, who has no idea who Torchwood is. She apologizes, admitting she's new, and Jack wishes her well. Lois logs the call from Torchwood and a red flag comes up. She uses Bridget's password to enter the proper security code to pull up the Torchwood file and determine they deal with extraterrestrial threats.
Frobisher and Dekker go to a high-security underground facility beneath Thames House and Dekker explains that they converted the readings to digital years ago and kept the original equipment. The equipment activated during the two trance incidents and they picked up a signal on the frequency 456. He's set the translators on it but warns it will take time. The 456 is open and Frobisher wonders why they would change. Dekker tells him to find out and says that the 456 goes beyond the Prime Minister. Frobisher wonders if he has children and Dekker admits that he doesn't, and that it's a godsend.
At the Hub, Gwen reviews footage from Taiwan and realizes that all of the children across the world is speaking English. Jack suggests that English is the dominant language but Ianto notes that Chinese is actually spoken by the most people. Gwen finds the footage of the one man, Timothy White, at the sanitarium in East Grimstead in England. Jack takes off and Gwen calls Rhys at the house he's looking at to buy them. He suggests that one of the rooms could be a nursery and Gwen tells him to drop it. Rhys also notes that the two incidents were timed around when children would be out on the streets in Britain, and that the incident was focused on Britain as the primary locus. Gwen admits it's a brilliant idea
Ianto and Jack realize that they need a child to test and Ianto admits he can find almost anything else. Jack gets up and goes, saying he'll see him later.
Frobisher reports to the Prime Minister who admits he's running a siege from above. The Prime Minister asks for suggestions and Frobisher suggests they remove certain historical events from the files so Britain isn't incriminated. He explains that they called the aliens the 456 based on their radio frequency, and admits that they have no idea if the 456 will remain quiet about their involvement. The PM says for Frobisher to make sure he's not involved and his name doesn't appear on any documentation. He leaves it to Frobisher to file Blank Page.
Jack arrives at the home of Alice Carter. She reluctantly lets him in and her son, Steven, runs up and calls Jack "Uncle."
Ianto goes to the home of his sister Rhiannon, who is surprised to see him. She's brought her children David and Mica home to be on the safe side and refuses to let him take Mica out for lunch. However, she invites Ianto to stay, says he's been seen, and insists that they have things to talk about.
Jack tells a skeptical Alice that he doesn't know what's going on. He asks if there's any word from her ex-husband Joe and Alice says that's he finally got married again and is living in Italy. Jack asks how she's set for money and Alice says it's easy to write cheques. He insists that he stays away because she asked him to, and he'd be glad to visit every day. She calls him "Dad" and admits that she can't stand the fact that he doesn't age while the rest of them keep getting older. Jack wonders if Alice is ever going to tell Steven that Jack is his grandfather, pointing out that he'll eventually figure things out. Alice says that's another reason for Jack to stay away. When Jack suggests he spend some time with Steven today, Alice realizes he wants him to test and say she won't let Steven near him.
As Jack leaves, he pages Rupesh and asks if there's a children's ward at St. Helens.
Rhiannon tells Ianto that her friend saw him having dinner with a gorgeous man. Ianto insists that Jack is his boss but Rhiannon doesn’t believe it and asks him to be honest with her. She notes that he left when their dad died and wonders if he blames her. Ianto insists that he doesn't and says that it's his job, and it's difficult. However, he admits that Jack is handsome and they're dating. She makes sure that Jack is nice and wonders how long Ianto has been dating men. Ianto admits that it's just Jack and Rhiannon promises not to say anything. However, her husband Johnny comes in and immediately calls Ianto "Gay Boy." He asks about Ianto's car and they hear the alarm going off. Ianto runs out and discovers that local thieves have stolen the car. Johnny figures they'll circle around and grabs a brick to throw at them when they come back.
Gwen talks to Timothy's nurse, who explains that Timothy has been and out of the sanitarium. He lived in Leeds for 40 years and was found living homeless on the streets after he disappeared at the age of 11. Timothy used to have a Scottish accent but it's disappeared. Gwen talks to him privately and asks if he remembers what he said. Gwen suggests it might have been aliens but Timothy initially denies it. She says she's met aliens and promises that she'll believe him and won't say anything to anyone. Timothy takes her hand and starts sniffing it. He realizes that she's telling the truth and she's met aliens. When he worries that the staff is watching him on the security camera, Gwen jams it and asks for his real name. He explains that he was a kid and somebody took him and the others out into the night. The staff they said they were going to a new home and drove them out into the Scottish countryside. Timothy saw aliens of light in the sky who took the other children, but he ran off. He warns that they're coming back and he's been smelling them in the air for months. Gwen offers to help and promises to find the records of the missing children. However, she needs to know his real name. He finally admits that his name was Clement McDonald from Holly Tree in Scotland. Clement sniffs at her and says that he can tell that she's three weeks pregnant. The nurse comes in to check out the camera before Clement can say anything else. As Gwen leaves, Clement offers his congratulations.
Gwen calls Ianto to have him run a trace on a Clement McDonald of Holly Tree. She doesn't believe it when he says someone stole his car.
The Home Office intercepts Ianto's record search for Clement.
Lois watches as Bridget meets with Frobisher. He tells Bridget he can find the names under 456 and gives her the Blank Page. She goes back to her desk, types briefly, and abruptly walks away. Lois logs in using Bridget's passwords and reads the Blank Page file. It's an order to kill four individuals... including Captain Jack Harkness.
Jack arrives at the hospital and Rupesh tells him that another Chinese man died. He came in with a nosebleed from a brain hemorrhage and died shortly thereafter. Jack examines the corpse and Rupesh shoots him in the back. He tells his assistant to seal off the area and orders soldiers in. They secure the area and take Jack away.
The Home Office monitors determine that Torchwood has found Clement McDonald at the sanitarium and order him brought in.
Operative Johnson arrives at the hospital and Rupesh wonders why he was ordered to blow his cover rather than infiltrate Torchwood. Johnson asks who killed the Chinese man and Rupesh admits that he did to set up Jack. Rupesh wonders if what they say about Jack is true, just as Jack revives. Johnson shoots him again but admits that they have no idea how he keeps coming back. They think it relates to the Rift. She slices Jack's stomach open while explaining that Rupesh's orders were changed due to the children.
At the sanitarium, Clement realizes that soldiers are moving in. He escapes outside and runs into the woods.
Johnson seals Jack back up and orders everyone out, and puts Jack back where he was. When Rupesh wonders how they're going to cover his involvement, he realizes that he won't be going with her and tries to make a run for it. Johnson shoots him down in the hallway and has his body hauled back next to Jack's. As they leave, Jack revives again and finds Rupesh's corpse.
At the Hub, Ianto locates Holly Tree orphanage and discovers that Clement was transferred out with the other orphans. Jack approaches the Hub as Johnson and her men watch him enter. Johnson tells her men to give him five minutes to get inside.
In the Hub, Ianto hugs Jack when he realizes he died. They go to tell Gwen, who is in the lab doing a check on herself. She confirms that she's pregnant just as Clement said. Jack wonders if it's good and Gwen finally admits it's brilliant. Jack notes that she told him before she told Rhys and Ianto offers his congratulations before telling them he lost the car. Gwen worries about her job and Jack assures her they'll manage. However, as he takes her hand atop the medical scanner, an alarm goes off. The scanner reveals that there's a bomb inside of Jack's stomach. Jack orders them both out and reminds Gwen that she's pregnant.
The children start chanting again. At home, Frobisher looks on as his two daughters begin their chant. Ianto's niece and nephew do the same.
Ianto tries to override the mechanism but Jack insists he can survive anything and shoves him out. They share one last kiss and then Jack sends Ianto up on the platform
Frobisher begs his children to stop.
Gwen runs to the surface just as an enormous explosion erupts from the Hub.
The children finish by saying "We are coming... back."