Sleeper was the second episode in the second series of Torchwood. As the title suggests, it dealt with the presence of sleeper agents having their conditioning activated, a crisis that revealed an unknown alien race was actively gathering intelligence on the Earth and might strike again one day.
Beth and Mike are a married couple who are awoken from sleep when they hear someone in their house. Mike grabs a cricket bat, while Beth calls the police. Two burglars enter their room, knock Mike out, and threaten Beth. An unseen, violent struggle occurs as a lamp by the bedside glows brighter and brighter.
The Torchwood team soon arrive at the couple’s flat, where one of the burglars is dead and the other severely injured. Tosh and Jack investigate the scene, while Gwen and Owen go to the hospital to interview the husband and wife, as well as the surviving thief. An officer at the crime scene and Gwen both suspect that the husband was responsible, citing the fact that he kept a cricket bat in the bedroom. Jack and Owen both suspect the wife though, with Owen claiming, “It’s always the one you least suspect.” Beth claims to remember nothing, however. Owen and Gwen stay until the burglar regains consciousness. Upon being questioned by Gwen, he confirms that “the woman” did it before he flatlines.
Beth is brought to the Hub’s interrogation room. Jack attempts to get her to confess, showing her the crime scene photos and questioning whether she might be covering for her husband, but to no avail. Although a body scan reveals nothing either, a power surge also occurred at the hospital while Beth was there. Owen then tries to draw blood from her arm, only for the needle to snap: twice in a row. He then breaks a scalpel against Beth’s arm with nary a scratch. Beth also claims to have never been sick. Having seen enough, Jack tells her to stop pretending she’s not an alien. When Beth claims that aliens don’t exist, he takes her to a holding cell and shows her a Weevil. While Beth continues her disbelief, the Weevil cowers at her presence. Unable to explain the oddities surrounding her, she asks Jack how she can prove she’s not an alien.
Jack decides to use a mind probe on her, despite Ianto’s objections that the head of the last alien they used it on exploded. Gwen comforts Beth as she’s strapped in. The mind probe begins, with Beth appearing in great pain. Gwen objects, but Owen assures her it’s safe and Jack tells them to go deeper, as Beth is still claiming to be human. The lights flicker and Beth’s heart rate rises and still Jack insists on continuing. Beth eventually passes out. But Jack’s persistence pays off, as Beth immediately sits up rigidly, the skin on her right arm transforming into a ridged formation — spotted with several glowing lights. Despite attempts to talk to her, she repeats the same words in an alien language, which Jack identifies as her name, rank and serial number.
Jack relates to the team what he knows about the species, which isn’t much, as they leave no survivors. The aliens, which he calls Cell 114, infiltrate planets by disguising themselves as the local inhabitants and relate information back to their superiors, with the sleeper agents being completely unaware. Tosh shows the team an implant inside Beth’s arm, where the data is stored, which is protected by a force field.
The decision is made to tell Beth what she is. She is quite distraught at the revelation, questioning whether her memories and feelings for her husband are even real. Gwen assures her that her humanity does not only lie in her body, but in her mind as well. Beth asks if they will kill her and if they have killed other aliens. Gwen tells her that they have, but only when in a “kill-or-be-killed” situation. Beth wishes that she had never found out and that she could live a normal life. Jack points out that she would change on the day of the attack. Beth protests that she is not that person. Jack disagrees.
Back in the Hub’s main area, the team debates what to do with her. Toshiko suggests freezing her. Although Jack objects that she could still transmit data, Tosh believes she can single out the transmitter and disable it.
As Jack and Gwen lead Beth out of her cell, the memories of her attack on the burglars begin to return. As she’s prepared to be frozen she asks that if they cannot figure out how to make her human, that she be prevented from hurting anyone, permanently, to which Jack agrees. Tosh concentrates an electromagnetic pulse on her arm and then Owen sedates her.
However, unbeknownst to the team, Beth’s implant reactivates, sending a signal elsewhere. Throughout Cardiff, seemingly ordinary people stop what they are doing as they are activated, abandoning their jobs and families, with some even killing their loved ones who try to stop them.
Back at the Hub, Beth wakes up in her cryo-chamber and breaks out of it, setting off alarms. Since her implant gathered information about the Hub, she is easily able to exit through the tunnels. Owen theorizes that her body merely projected what they expected to see and that her vital rates did not drop to zero as they believed. Jack does not think Beth has activated, as she could have killed them all if she had.
Beth has gone to the hospital to say goodbye to Mike. She tells him she will only hurt him if she stays. He protests as she hugs him that nothing she could do would be worse than her leaving him. They are both surprised at a sudden sound and look down to see that Beth’s arm has morphed into a spike, which is now protruding from Mike’s chest. Distraught, she calls for help. Jack and Gwen arrive and take in the scene. Beth insists it was an accident. Gwen scans Beth’s arm to check that it’s safe. When Beth refuses to leave Mike, Jack and Gwen are forced to drag her out of the room before hospital staff arrive.
Elsewhere, Patrick Grainger, the leader of the local council, begins his day with his family. When the doorbell rings, he goes to answer the door. One of the sleeper agents, David, is at the door. After confirming Patrick’s identity, David morphs his hand into a spike and runs Patrick through with it repeatedly, in front of Patrick’s family. Patrick’s wife begs for the lives of her children, but David makes no reply other than to stab her husband one more time and leave. Meanwhile, another sleeper uses a fuel tanker to destroy both a motor way and an underground fuel pipeline used by the military in emergencies.
Torchwood realize that more sleepers have activated and scramble to coordinate a plan. However, the team is cut off from one another when another sleeper destroys a telecommunications station. Jack and Gwen urge Beth to try to connect with the other sleepers so they can prevent more deaths. She activates her implant and tells them that only one remains: David.
While Owen, Gwen and Tosh are panicking at the lack of communications, Jack rigs up a CB radio to contact them with. He tells them David is heading for an abandoned farm and that he needs to know why. Ianto and Tosh’s research reveals that there is a stockpile of ten nuclear warheads stored in a mine shaft at the farm. Jack theorizes that this is how the cells are so effective: they use the weapons of the people they conquer against them. As the team in the Hub ponders what will happen if Jack and Gwen don’t reach the sleeper in time, Owen suggests that they all have sex. Ianto bemoans that the end of the world has become worse.
David arrives at a military compound and decimates the soldiers guarding it, as they are unable to fell him with bullets. His way cleared, the sleeper proceeds to break through the entrance’s security codes with ease. As he breaks through the final lock, Jack runs David down with the Torchwood SUV. Nonetheless, David gets back up and stabs Jack through the chest, taunting him that they know all about Torchwood and that they will be factored into the invasion plans. Gwen uses the scanner to disable David’s transmitter and shielding. Pulling himself off the blade, Jack shoots David and demands to know when the others are coming. David claims that they are there already. Laughing madly, he detonates his suicide implant, as the others run to get clear.
Later, Gwen and Beth are in the Hub, preparing for Beth to be frozen. Beth claims that while the guilt of what she has done is horrific, what she fears more is losing it and becoming an uncaring murderer. She thanks Gwen for being so kind to her and wants her to remember her for who she was. Beth then morphs her arm into its blade form and holds it to Gwen’s throat. As the team all surround them, guns drawn, Gwen tells them that it’s a trick; that Beth wants them to kill her. Beth denies this, claiming that she will kill every human. As she raises her arm as if to strike, the team all fire at her, killing her. Gwen protests that she would not have hurt her. The team assure her that they couldn’t take that risk and that Beth knew that. Jack comforts Gwen as she looks on Beth’s body.
That night, Gwen and Jack discuss Gwen’s upcoming wedding and whether or not they stopped the invasion. Gwen believes that even if they have not, they know more now than they did and that they can fight.