People gather to see a travelling carnival. The barker, Ghostmaker, assures people they will never forget it for the rest of their lives. He offers one girl a ticket and after a moment's hesitation, she runs in. However, when her mother turns at the sound of a scream behind her, she looks back and discovers that the carnival has disappeared along with the girl.
Jonathan Penn is splicing old black-and-white video footage of Hope Street at his flat when Ghostmaker appears on his screen. Jonathan has no idea how it appeared there. The windows suddenly burst open and when Jonathan shuts them and goes back to the monitor, he discovers that Ghostmaker is still on the screen despite the fact the film has run out.
At the Hub, Jack hears the sounds of a pipe organ and a screeching noise from within the city and recognizes it. When Tosh arrives out of the rain, Jack asks her if there's a travelling fair in town. She says that it's unlikely with the rain, and tells him that Ianto, Gwen, and Owen have gone to the cinema for opening night because the building has a record of rift activity. When Tosh turns, she discovers that Jack has left.
Gwen, Ianto, and Owen walk through the rain and arrive at the cinema, the Electro. As they go in, the owner, Dave Penn, wonders to his wife where their son Jonathan is with the film they need for the premiere. Meanwhile, Jonathan runs through the rain on his way to the cinema and Jack drives there at top speed.
As they go in, Ianto explains that his father used to bring him to the Electro on Saturdays. Behind them, Jonathan arrives with the film and Dave sends him up to the projection room. As Jonathan take the film out, he hears pipe organ music. He pauses for a moment but then starts to put the film.
Dave gives the opening presentation to the sparse crowd, explaining they can see the cinema and Hope Street as it once was. Jonathan begins the film Owen and Gwen starts to chuckle at the old footage and Ianto tells them to be quiet, However, the images of the fair start appearing again, including Ghostmaker. Dave runs up to the projection booth and Jonathan says he has no idea how the footage got there, and the machine won't switch off. In the audience, Ianto claims that he saw Jack on the film. as it repeats the same scenes over and over. However, before it can repeat again so he can confirm it, the film breaks. As Owen and Gwen leaves, Ianto sees two shadowy figures on the wall.
Jack arrives and Ianto tells him what he saw, the shadows and Jack on the screen. Before they leave, Jack admits that he heard carnival music, and that the cinema killed off the travelling shows.
At the Hub, Tosh monitors the computers and notices a power fluctuation. She hears the same fairground music that Jack mentioned earlier.
A girl is at the Chain Lane bus station in the rain, calling home to tell her mother she'll be late. Ghostmaker and a carnival woman, Pearl, walk toward her, the woman embracing the water on the ground. They offer her a ticket and suggest she join the show... forever. Ghostmaker touches her face and the girl gasps as the breath from her body pours out from her mouth and into a silver flask that he holds to capture it.
Jack and Ianto talk to Jonathan, who explains what happens. They confirm the projector works normally now and he explains that he's been compiling footage of Hope Street and the Electro. He's never seen the circus footage before, and admits he heard organ music and smelled the odor of bromine or iodine, like the film itself. Tosh calls to inform Jack about the peak in rift activity at the Electro, and tracks it to Chain Lane, running parallel to Hope Street. The team drives there and discovers the girl, seemingly dead despite the fact she has a heartbeat. Her mouth is dried and withered and she has no saliva.
Ghostmaker and Pearl approach a cafe and Pearl tells Ghostmaker to make the owner cry so she can feed on her tears.
The team gets the girl to the hospital and Owen explains to Jack that something drained most of the moisture from her body. The paramedics arrive with the restaurant owner, who is in similar condition. Jack figures that some part of them, their life force, has been taken from them. The team returns to the Hub and watches the circus footage. Jack recognizes two of the members and they finally find footage of Jack. He realizes that they're the Night Travellers, who only performed in the dead of night and left a trail of damage and sorrow wherever they performed. When the travelling shows faded away, all people had to remember them were the film clips. Ianto has Tosh run it frame by frame when he realizes something's missing. He calls Jack over and explains it's not the same one they saw at the Electro. Pearl and the Ghostmaker are both missing from the footage but were in it at the Electro. Jack figures that when Jonathan ran the film, the two Night Travellers escaped the film. Jack tells them to find witnesses and evidence from the pas and tells Ianto to come with him to the conference room.
As the team tracks down the information, Jack explains to Ianto that no one knew when the Night Travellers were coming. Jack was with a small company and was sent to investigate rumours of the Night Travellers. He joined the show as "The Man Who Couldn't Die."
The Ghostmaker announces the Joshua Joy Travelling Show and presents its members, including Pearl, who lives in the water and sleeps beneath the waves.
Ianto brings up files on other old cinemas but they've been torn down or converted. Tosh picks up a reading of the sea except its inland, running through the centre of town.
A family of four is driving along when the father sees Ghostmaker and Pearl in the road ahead. He brakes to a stop but they disappear. Ghostmaker appears at their window.
Jack wonders if the Night Travellers are fighting back against the cinema that contributed to their destruction. They conclude that they're looking for a new audience. Tosh tells them what she's found, the sound of waves and seagulls, but it disappeared as suddenly as it came. Jack wonders what the Night Travellers are up to.
In an empty pool, Pearl is dousing herself with water while Ghostmaker listens to the spirits confined within his flask. He tells Pearl that they have six and she wants to see the air that their new audience breathes. They listen to the last breaths trapped within the flask and Pearl asks if they can bring the others so that they're all together again and can travel and perform. Ghostmaker agrees but explains they need the rest of the film.
The next morning, Jack and Ianto go to the hospital when the family is brought in, in the same cataleptic state. When Jack comments how the Night Travellers came out of the rain, the nurse remembers that a patient at a psychiatric hospital said the same thing. The patient, Christina, had been there since childhood and was always terrified when an entertainment show came to town. Jack and Ianto talk to the elderly woman, who explains she was a child when she saw the Night Travellers. She describes Ghostmaker and Pearl.
At the pool, Pearl douses herself repeatedly and then checks in a room where the spirits of the people they've all taken are standing, motionless.
Christina talks of how Ghostmaker wanted her to join the show and held the silver flask. He offered to take her breath so she would be in his audience forever. She ran, but many of the others in her village disappeared that night.
Back at the Hub, Gwen traces a series of related disappearances and persons deprived of their breaths and left in comas. They realize they need to find the flask and save Ghostmaker's victims.
Jonathan returns to his warehouse loft and finds the door open. He goes inside and finds the bathtub running over with water. He goes it and finds Pearl lying inside. She reaches up for him, grasping him for a second, and he runs out the door as the Ghostmaker watches. He tells Pearl they have the film and its time to bring the others. Outside, Jonathan calls Jack and tells him the Night Travellers are there. Jack, Ianto, and Owen arrive arrives but the Travellers have disappeared.
At the Electro, Dave and his wife Faith arrive and hear the piano playing. They go into the auditorium and see Pearl approach them and invite them in.
Jonathan realizes that all of his circus sideshow films have been stolen, and the team realizes that the Night Travellers plan to bring the others through. Jack calls Gwen and tells her to meet them at the Electro. the same odor of developing film is in the air and Jonathan describes Pearl's hand as feeling like a piece of film. Jack realizes they've become part of the film and suggests that they film the Night Travellers and trap them, and then expose the film to as much light as possible to erase them once and for all.
The team goes to the Electro and finds the doors locked. Jonathan unlocks the doors and they go into the auditorium. Dave and Faith are in a trance, forced to provide the circus with an audience. The curtains open and Gwen gets Jonathan out while Owen goes upstairs to see who is running the projector. The circus footage begins again and the other Travellers begin to emerge. Jack films the event as it occurs and Pearl informs them that the entire city belongs to them. She sees Jack and Ianto as they back out.
Upstairs, Owen tries to get into the projector booth and the Ghostmaker emerges. He tries to drain Owen's breath but discovers that he's dead and casually dismisses him as of being of no use. Ianto manages to grab the flask from him and runs outside. He runs down the street into an alleyway but Ghostmaker catches up to him and takes the flask. He opens the stopper on the flask and throws it into the air. Jack exposes the film, destroying Ghostmaker and the others. Ianto manages to catch the flask before the breaths can escape. The spirits disappear from the pool and all the victims die. However, there is still one breath trapped in the flask and Jack wonders who they saved.
Jack and Ianto go to the hospital where the doctor explains that only the boy from the family survived. Jack gets the boy out of the bed and opens the flask, giving the boy his last breath back. He revives and smiles.
Later, Ianto destroys the remaining circus film and hopes that's the end of it. Jack worries that there might be some film out there and the Night Travellers are still trapped, waiting.
At a rubbish sale, a father and his son find a canister of film. As they go, the boy drops the film briefly and Jack hears the organ music as he locks the flask away in the vault.