The Torchwood SUV races through the streets of Cardiff and screeches to a halt outside a disused boarded-up building in Sage Street. Tosh finishes a phone call (in Japanese) and is wearing very smart evening wear because it’s her grandfather’s 88th birthday today and she‘s about to leave for London for the family celebrations, but Jack pretends to be disappointed as he’d thought she’d made the effort for his benefit. Although the Ritz Dance Hall has been derelict since 1989, they’re here to investigate complaints that music from the 1940s has been heard drifting out. As Jack goes upstairs, he momentarily hears the music, then it fades away just as suddenly. They arrive in the main upstairs dance area and Jack admires the old-fashioned chandelier, recalling the days of dashing young soldiers and pretty young ladies. He takes Tosh’s arms and leads her in a dance, but she’s concerned about the possible damage to her laptop. They finish looking around, but are satisfied there’s nothing here but memories and dust…but as they make their way downstairs, they hear the band music again. They rush back up to the main dance floor - and discover everything is exactly as it was in the 1940s. The floor is filled with young officers in Second World War uniform dancing with young women, there are patriotic flags hanging from the ceiling and a band is playing. Jack and Tosh move through the crowd and she comments on how real everyone looks, but Jack has news for her. These people aren’t ghosts - there’s been a temporal shift and they’re both back in the real 1941. Jack thinks it’s beautiful, but Tosh wants to leave, so they head for the main entrance. The door is opened for them by the elderly Manager, Bilis Manger, who invites them to call again, but as he closes the door behind them, Bilis’s smile fades. Outside, it’s night time and Jack and Tosh discover the SUV is missing. The street itself is also adorned with Union Flags and other patriotic bunting, and Jack spots a poster for that night’s ’Kiss the Boys Goodbye Dance’ at the Ritz - and realises the date is 20th January 1941...

Owen is asleep on the couch in the Torchwood Hub when he’s woken by an electronic bleeping. He stares bleary-eyed at Ianto who tells him the sound is coming from Tosh’s computer, which was set to monitor for any further movements in the Rift. It’s been opening more and more recently and Tosh believes the equations are forming some sort of pattern, but it’s all a bit over Ianto’s head so he tries calling her to see if she’s getting any readings at her end. Owen wonders why he hasn’t been briefed on any of this, but Ianto simply says it’s because he’s been off recently. There’s no reply from either Tosh or Jack, so he calls Gwen and asks her to go to Sage Street to see if she can find them and get access to Tosh’s files.

In 1941 Tosh tries calling the Hub, but the line is dead. Jack suggests they go back inside the Dance Hall as that’s where they crossed over. Tosh is worried they might never get back, but Jack reminds her that flotsam and jetsam slips through all the time. She becomes angry at his lack of concern and points out that the group back in the Hub won’t be able to help as she has all the necessary readings on her. Her anger attracts the attention of some bystanders and Jack suggests they try to blend in with the crowd. Tosh knows this won’t be easy as she’s the only Asian here. Jack and Tosh go to the bar and they’re approached by a young RAF officer named George who tries to chat Tosh up. When Jack realises he hasn’t got the right kind of money to pay for the drinks, George steps in and buys the round. He asks for only one thing in return - and drags Tosh onto the floor for a dance. Jack is amused, but a young woman, Audrey, looks on in disgust, wondering why he would be dancing with a ‘Jap‘.

Owen manages to get into Tosh’s file and accesses all her recent reports, right up to Christmas Eve, the day Diane flew through the Rift. He’s starting to wonder whether Tosh has discovered a way to open the Rift deliberately, in which case they might be able to get Diane back. Ianto points out that Jack would never allow that as opening the Rift could devastate the entire city. Gwen arrives in Sage Street and finds the SUV still parked up outside the derelict building. She goes inside and calls out for her friends, but there’s no reply. When she reaches the upstairs dance floor she thinks she can hear 40s music, but it quickly fades away. She calls out for Jack again…

…and in 1941 Jack momentarily hears his name being called. He decides to rescue Tosh who’s looking extremely embarrassed on the dance floor. He taps on George’s shoulder, but the officer is reluctant to let Tosh go and says he’s only ‘borrowing’ her. When George becomes aggressive, Jack asks if he’d prefer to dance with him instead - and George starts pushing Jack. He tries to ignore it, but then George punches him and it looks like a fight will ensue, but eventually it’s stopped by the arrival of a tall, handsome American Captain who explains that his men are a bit lively tonight as it‘s their last night before they fly out again. He orders George to apologise, first to Jack and then to Tosh. As Jack heads back to the bar, the Captain approaches him and asks if he’s a volunteer too. They both go to introduce themselves at the same time - but then Jack allows the other officer to go first…which is just as well, because he introduces himself as Captain Jack Harkness of the 133rd Squadron. Both Jack and Tosh are stunned by this news, and just at that moment Bilis calls for their attention and takes a photograph of the two men shaking hands.

In the Hub boardroom, Ianto watches as Owen spreads a pile of documents across the table. He discovers the Ritz Dance Hall opened in 1932 and shut down in 1989. It’s due to be demolished in one week’s time so it’s odd that the ghostly music from the 1940s is only being reported now. He flicks through some more of the records and newspaper clippings - but it’s Ianto who discovers the photograph of Jack and Tosh shaking hands with the American officer.

Bilis insists on one more photograph for the record, and he stands between the two Captain Jack Harknesses while another picture is taken. Jack tries to leave, but the real Captain Harkness stops him and asks for his name. Jack pauses for a second, then introduces himself as Captain James Harper from the 71st, which by coincidence is where Captain Harkness says he’s due to be posted next. He offers Jack and Tosh a drink, but they make an excuse to leave. In the corridor, Tosh demands to know why the other man has Jack’s name and accuses him of holding out on her. Jack admits that it’s not really his name, it’s the other man’s name and he simply adopted it, although he didn’t realise how ’hot’ he was. Jack says he knows too much and when she asks him to share, he says she really wouldn’t want to know. He asks what she’s carrying on the laptop and she says it’s half of the equation with the other half back at the base. If she can find a way of getting her half back to the others, they can combine them to open the Rift and get them back.

Gwen is still searching the corridors. She heard the music earlier, so she guesses that they might be able to hear her too. She calls out their names… …and in 1941 Tosh hears her, but when she turns round there are only other people from this time. Jack and Tosh find an empty room where they can work in private. As she starts setting up the laptop, Jack looks around and realises they’re in the Manager’s office. Unfortunately the battery on the computer is beginning to run low, so Tosh has to write down everything she can before it dies. Eventually the power fades completely, but she has everything she needs. All she has to do now is get the exact ordnance of the dial source so she can integrate them to the wave-form equation which they’ll need to get back to the Hub. They’re interrupted by the arrival of the Manager Bilis, who demands to know what they’re doing here and why Jack isn’t in full uniform. Jack tells him he’s on leave for 48 hours. Tosh has noticed Bilis’s unusual camera and the Manager explains that it can take photographs ’instantly’. She’s surprised that cameras can do that, but Bilis responds by expressing surprise at her ’attaché case’ which is made out of metal. The clock in the room strikes 9.30pm and Bilis tells them they should leave, but as soon as they’ve gone, he opens the desk drawer and removes a file marked ’Torchwood’.

Gwen leaves the building and calls the others to tell them she’s had a good look around, but most of the doors were locked. Suddenly she hears 1940s music again and while she’s distracted, a figure appears behind her and asks if he can help. She turns round and meets the caretaker, Bilis Manger - who looks exactly the same as he did back in 1941. Gwen asks if he would mind opening the building up to her as she thinks some of her friends might have got locked inside. He agrees and invites her back inside.

Tosh is getting increasingly worried about being stuck in 1941 because of Pearl Harbour, but he assures her that doesn’t happen until the end of the year. She remembers her grandfather being in London at the time and he was persecuted, but Jack promises to take care of her. She realises he fits into this period very well and she asks him if he’s been here before. He admits that he has - in fact, he served during the War but he was undercover and needed a false identity which is why he took Captain Jack’s name. She wonders who Jack was before that, but he doesn’t answer. He says he only chose the Captain’s name because it was convenient and Tosh realises this means the real Captain is going to die in battle. Jack confirms that this will happen tomorrow.

Jack and Tosh join the real Captain Harkness, who’s enjoying a drink with some of his fellow officers. She asks them which of the group is the best navigator and George points to another colleague, Tim, who’s a very poor pilot but at least he’s guaranteed to know exactly where he is if he ever goes down. Tosh invites Tim away for a private chat and as soon as he’s gone, the others laugh and joke about how far he’s developed in the last five weeks. The Captain is pleased to see Jack again and invites him for a chat while Tim fills Tosh in on the missing information she needs to complete the equations. Jack makes conversation with the Captain and George, who asks about the action they’ve seen recently. He boasts about the Captain’s success rate in the Battle of Britain and the fact that he hasn’t lost a man yet, but the Captain doesn’t seem to want to talk about. He goes to the bar to buy another drink and a young woman named Nancy approaches him. Jack notices that the two of them are obviously an item, but the Captain didn’t expect her to be here tonight and he seems uncomfortable.

In the present day, Mr Bilis shows Gwen around the rest of the derelict building and they eventually find themselves in the cellar. He asks her what her friends were doing here in the first place and she tells him it was just a silly dare as someone said it was haunted. He says she looks worried, so he offers her a cup of tea and she follows him out of the cellar. He casually asks whether anyone is expecting her and when she instantly says yes, he suggests she calls them in case they start to think she’s disappeared too. He goes into a side room to fill the kettle and Gwen take the opportunity to contact Ianto for news. He’s not found any more photographs of Jack or Tosh after the night of the dance, which is encouraging - although Owen points out that they may have been killed by a bomb. However, Ianto mentions the name of the manager, Bilis Manger, and they realise he has the same name as the current caretaker. She says he’s not old enough to be the same man, although he does look oddly ’out of time’. She describes him and Ianto compares it with the old photographs from the War and they realise it is indeed the same person! Owen tells Gwen that Bilis must have come through the Rift too, so he asks her to find out what he’s doing there, but Ianto orders her to get out straight away and wait for their backup. Ianto and Owen argue about whether it’s a trap, and while they’re distracted Gwen takes the initiative and leaves.

Jack finds Tosh and she tells him she has everything she needs. All she has to do now is find a way of leaving a message for the others so they can find it back in the present day. As they turn to leave, Audrey - the woman who called Tosh a ‘Jap’ earlier - steps in front of Tosh and asks who she’s with. George tells he she’s been with Tim having a boring conversation about navigation - and the woman suggests Tosh might be a spy. A small crowd gathers around them and accusations start flying. Audrey demands to see what’s in Tosh’s bag and tries to grab it off her - but Jack steps in and pulls her off. He tells her Tosh is a decoder for the Brits and the contents of the bag are top secret. Captain Harkness also steps in and proposes a toast for Tosh, for without her they’d have no way of defending the country. The crowd disperses and Tosh tells Jack she needs to get Bilis’s camera to take photographs of the equations. Jack is about to go with her, but the Captain arrives with a drink for him and asks him to stay. The two men start to talk and the Captain tells Jack he’s been resting recently after he injured his back bailing out over Kent. They’re interrupted by the return of Nancy who asks if she can join them.

In the manager’s office, Tosh uses Bilis’s camera to take a photograph of the equation - and she’s caught red-handed by Bilis who tells her the camera is very unusual and rare…not unlike herself. She hides the photo, but in her hurry to leave she forgets the equation. Bilis spots it and hands it to her, commenting that he can think of much better things to photograph than numbers.

Back at the Hub, Owen starts dismantling some of the floor plates and pulling out cables linked to a device called the Rift Manipulator. Ianto tries to stop him, but Owen insists they should go ahead even though they’ll have to improvise around the missing numbers. Ianto argues that it’s took risky and if they make a mistake, anything could happen. Owen reminds him that their friends are stuck in the middle of the Cardiff blitz and bombs are falling all around them and he sees it as his duty to get them out. Ianto knows that if they open the Rift now, the whole world could suffer - they might all get sucked in and nobody knows what might come out. He realises this is really about Diane and he tries to convince Owen that she chose to leave him, but Owen retaliates by reminding Ianto about the lengths he went to to save Lisa from being turned into a Cyberwoman. He accuses Ianto’s girlfriend of being a screwed-up metal monster who tried to kill them all, but Ianto argues that he loved her, whereas Owen only knew Diane for a week. Owen ignores him and continues installing the cables into the Manipulator. Unfortunately it doesn’t seem to be working, which pleases Ianto as Jack would never want them to use it in this way. Owen examines the device and realises there’s a vital piece missing.

The two Jacks and Nancy are sitting quietly at a table. The atmosphere is frosty as Nancy is starting to feel left out and unwelcome. The Captain asks Jack about his next mission, but he responds by reminding them that careless talk costs lives. Nancy gets up to leave and Jack apologises for giving the impression that he meant her, but she says she’s leaving now so that she can get a lift home. The Captain tells her he needs to stay and she’s disappointed because she knows he’s leaving tomorrow night. He gives her a peck on the cheek and says it’s been a good few weeks and he’ll be in touch next time he’s on leave - but Jack realises she’s heartbroken and was expecting more of a commitment on their last night. The Captain sits back down and tries to justify himself by saying Nancy is a sweet kid, but he needs to look after his men tonight. Jack implores him to go after her and kiss her goodbye - because anything can happen tomorrow… The Captain assures Jack it’s just a routine training exercise, but Jack tells him that most people get caught when they’re least expecting it. No one knows what lies ahead, so he should kiss Nancy goodbye properly. The Captain eventually goes over to the cloakroom and kisses Nancy. She whispers in his ear that she loves him, but he looks shell-shocked. He returns to Jack at the table and tells him what she said and because of Jack’s advice he’s just made things twenty times worse. He walks off angrily.

Jack chases after the Captain and argues that Nancy falling in love with him is hardly his fault. He says it’s OK to play cool in front of his men, but there’s no need to do that in front of him. He tells him there’s nothing wrong with being scared, but the Captain responds by saying he has a duty to keep his head. Jack insists that a good Captain should explain the risks to his men and tell them what to expect, but the Captain can never forget listening on the radio to a young pilot who got shot in mid-flight, and hearing him screaming and yelling for his mum as the enemy pumped him full of bullets and ripped his plane apart. Jack knows how he feels. He went to war when he was just a boy and was with his best friend when they got caught crossing the border over enemy lines and they tortured his friend rather than him because his friend was weaker. They made Jack watch him die, and then they let him go. The Captain asks him which enemy he’s referring to and he says they’re the worst possible creatures you can imagine. Jack admits that he persuaded his friend to join up because he thought it would be an adventure.

Tosh leaves the Ritz and sits on the steps outside. She seals the photograph of the equation inside the plastic envelope she had for her grandfather’s birthday card. She hopes Gwen likes treasure hunts… …and back in the present day Ianto and Owen are using the CCTV cameras outside Sage Street to watch out for Bilis leaving the area. There’s no sign of any movement, so Owen puts on his coat and leaves, telling Ianto that Bilis must know how the Rift works, so he’s going to the dance hall to get some clues. Gwen leaves the Ritz and stands on the steps where Tosh sat 65 years earlier. She tries to work out how Jack and Tosh would try to help them - and then suddenly she catches a glimpse of Bilis walking around the corner. She goes to follow, but he seems to have vanished completely. The door to a nearby electricity substation is ajar and there’s a padlock on the ground. She looks inside and finds Tosh’s photograph, still inside the plastic envelope. She contacts Ianto and reads out the figures, but when he inputs them onto the computer he realises there are still some missing… …and back in 1941 Tosh is storing the photograph inside the substation when she realises there are some figures missing where she accidentally cut off the top of the paper when she took the picture. Just then, the air raid siren goes off and she realises there are enemy planes on the way. She races back inside the dance hall.

The dancers inside the hall start to panic and scream as they hear the sound of bombs going off in the distance. Bilis and Captain Harkness start to organise everyone into the bomb shelters while Jack calls out for Tosh. She finds him and as they head to join the others, she tells him about the problem with the photo. Everyone is evacuated into the cellar and there’s relative calm as people grow accustomed to the sound of explosions going off. Tosh tells Jack that it’s no good leaving a message in pencil as it will fade over time, so she needs to find something else. She searches the cupboards at the back of the cellar and finds an airtight coffee tin, which she empties. She deliberately cuts herself and then starts writing figures on her grandfather’s birthday card in her own blood. Meanwhile, the rest of the party are kept entertained by the band and the singer performing “There’ll be Bluebirds Over the White Cliffs of Dover”.

Gwen returns to the front of the Ritz and notices Owen’s car is parked nearby. She calls him and he tells her he’s already inside and is looking for Bilis’s office. While she keeps looking outside, Owen searches through the manager’s office, trashing everything in sight as he desperately looks for clues. Eventually he finds a locked safe and he uses an alien device to open it. Unfortunately it’s empty! Then he hears the clock chiming and it occurs to him for the first time that the office is filled with different kinds of timepieces. He opens up a grandfather clock in the corner and realises that the object at the end of the pendulum is the missing piece from the Rift Manipulator back at the Hub. As he leaves, he meets Gwen in the corridor and tells her he didn’t find any equations so he plans to return to the Hub while she keeps looking here.

In the cellar, Captain Harkness seeks out Jack and admits to him that he’s scared. The two men look at each other silently. Tosh seals the message away in the coffee tin… …and back in the present day Gwen returns to the cellar for a more thorough search. Once again, she’s distracted by the ghost-like sound of the singer, but the sound disappears just as quickly as it started… …and back in 1941, the air raid siren blares out again. Bilis switches on the cellar lights and invites everyone back upstairs for the dancing to continue. Tosh has finished just in time and the rest of the equation is now safely hidden in the cupboard. Tim notices her hand is bleeding and she tells him she slipped, so he goes to get a first aid kit from his van. George offers Captain Harkness a drink, but he asks for a few moments to have a private word with Jack. Once they’re alone, the two men just smile at each other… …and Gwen discovers the hidden card with Tosh’s equations, tucked away inside the coffee tin. She contacts Ianto and starts reading the figures out to him.

Owen returns to the Hub and gets the good news from Ianto. Unfortunately they input the equation on the computer and realise they’re still missing three figures. Gwen realises the last three numbers on the card have been deliberately scrubbed out. (Back in 1941, Bilis Manger discovers the card and erases the key figures). Tosh has also written a message at the end of the note in her own blood, asking them to tell her family that she loves them. It’s clear that Tosh is not expecting to return home to her own time…

In 1941, the dance starts up again and the party atmosphere soon returns to normal. Jack and Captain Harkness are looking down at the dance floor from a private table on an upper level. The Captain asks Jack why he sent him back to kiss Nancy goodbye and Jack tells him he should live every night like it’s his last and make tonight the best night of his life. The Captain is beginning to suspect that Jack knows more than he’s saying, and agrees that perhaps he should go to Nancy after all. He then asks Jack if he and Tosh are together and Jack admits that he has no one special in his life. The Captain leaves to find Nancy and Jack sits alone thinking…

Ianto watches Owen in horror as he tries to finish setting up the Rift Manipulator. He’s sure it won’t work with the piece missing - but Owen reveals that Bilis had it all along! Although they still don’t have all the equation, he’s hoping that the machine can work out for itself what’s missing. He switches on the device, but it doesn’t work. Owen races to Jack’s office and searches for anything that might give them better instructions on how to operate it. Ianto tells him he has no right, but Owen insists that he’s second-in-command and has every right to make decisions now that Jack isn’t here. He finds an old diary that contains a clue to the combination of Jack’s safe, which he opens. He removes several items and then eventually finds a file marked ’NOT FOR USE’. Inside are all the blueprints for the Rift Manipulator! Ianto and Owen stare at each other for a second - and then there’s a race to get back to the machine first..

The Captain tentatively returns to Jack, who’s still sitting alone at the table. Jack reminds him this could be his last chance, and the Captain admits that’s why he came back. They look at each other and an unspoken understanding passes between them. Jack says he might have to leave before the evening is over, so the Captain reminds him to make the most of the moment. He takes Jack’s hand - and then suddenly they both stand and separate as another officer and his girlfriend run onto the balcony. The girl asks if they can have the ’lover’s corner’ to themselves and the Captain makes an excuse about discussing strategies with Jack. Jack suggests he and the Captain go somewhere else, but Harkness says he’s already told him all he needs to know.

Ianto and Owen fight over the blueprints. Owen stresses that these are the very instructions he’s been looking for, but Ianto believes Bilis deliberately wanted him to find it in order to create total chaos and destruction. All the reports they received about the haunted dance hall were anonymous so it may have been Bilis himself who laid the trap. He pleads with Owen to listen to him, but Owen is tired of being in awe of the Rift and tired of living with Jack’s secrets. The two men start to fight and Owen ends up kicking the motionless Ianto while he’s on the floor.

Tosh joins Jack, who’s watching the dance alone. He tells her that tomorrow will be these men’s last training exercise. It should be just another day, but they’ll go out on a sortie and be surprised by two squadrons of Messerschmitts. The real Captain Jack Harkness will destroy three of the enemy and his men will listen to his whoops of joy over the radio - then it will all go quiet. He won’t be able to bail out because his whole plane is on fire. Jack admits to Tosh that he’s really a conman - that’s why he took Jack’s name and falsified the records so that it seemed he was still alive. She asks how he ended up at Torchwood and he explains that someone saved his life and brought him back from death. Ever since then, it’s like they’ve been keeping him for something and he doesn’t know what it is. He apologises for dragging Tosh into this and promises to look after her, but he starts to cry when he realises there’s nothing he can do for the real Jack.

By the time Owen has finished installing the missing piece of the Rift Manipulator, Ianto is watching silently. Then he orders Owen to put the key down. Owen turns round and sees Ianto facing him with his gun drawn. He tells him he has to let Diane go, like he did with Lisa, but Owen refuses to compare himself to Ianto. He dismisses him as ”just the tea boy”, but Ianto knows he’s much more than that. He believes Jack needs him, but Owen says that’s only in his dreams and really he’s just Jack’s part-time shag. The Rift has taken Owen’s lover and the Captain, so he considers it his duty to beat it. He places the missing piece inside the Manipulator - and Ianto opens fire and shoots him in the shoulder. The machine starts to operate and Ianto looks on in horror…