Amy, Rory and the Doctor split up to look for George. The Doctor knocks on one door and talks to an old woman, Mrs Rossiter. Rory talks to the landlord of the flats, Jim Purcell. Amy meets a pair of twin girls and their mother. The results are all the same; the residents slam their doors in the faces of their inquisitors. Amy and Rory walk past George's window just as the little boy peeps out. Rory says, "Maybe we should let the monsters gobble him up." And the boy shuts the curtains and opens them again after they have passed. The Doctor sees George looking out of his window and knocks on the door of the flat. George's father mistakes the Doctor for a health visitor or social worker and invites him in.
Amy and Rory get in a lift. The sound of the lift scares George. He whispers, "save me from the monsters." The lift plunges and Amy and Rory scream. The lift reaches the ground floor and the doors open but the lift is empty.
Mrs Rossiter takes a sack of rubbish out across the yard to a huge pile of black bin bags. She hears something move inside the pile and thinks it might be George trying to frighten her. Suddenly, she is sucked into the pile.
Amy and Rory find that they are in a house, but Rory suggests they have died. They find a lantern to help them see around them and, curiously, a wooden frying pan painted to look like copper. In a drawer is a large glass eyeball.
Alex tells the Doctor that George is scared of everything and that he and Claire have started a routine with George where anything that scares him is put in the cupboard. The Doctor goes to meet George, who asks if he has come to take him away. The Doctor, confused, says no. Instead, he suggests that they open George's wardrobe but they are interrupted when the landlord arrives and demands Alex pays the rent. George peers out of his room, scared of the landlord and his dog. The Doctor tries to distract and amuse George by switching on his toys with sonic screwdriver. This works and the Doctor scans George's wardrobe for monsters. The readings are not what he expects; in fact they are "off the scale." When Alex comes back in the Doctor tells him that George's monsters are real.
Amy and Rory find a room in the house where the door has handles and the hands on a clock are painted on. They are disturbed by a child's giggle. Elsewhere, Mrs Rossiter shuffles through the corridors, scared and alone. They look for the source of the giggling and open a cupboard door to find a large wooden doll. As they turn away in relief, the doll comes to life.
The Doctor overcomes Alex's objections about the reality of monsters by explaining that he has travelled across time and space to answer a distress call. Then the Doctor persuades Alex that they need to open the cupboard before changing his mind and then changing it back. As they do this, Purcell is sucked through the carpet of his flat. The Doctor opens the wardrobe but it is perfectly normal inside. Realising he is missing something he picks up a photo album of Alex and Claire. The photographs, taken eight years earlier and only weeks before George was born, clearly show Claire is not pregnant. Alex remembers that Claire can't have kids. The Doctor asks, "What are you, George?" the wardrobe doors open, revealing a doll's house. The Doctor and Alex are pulled into the wardrobe while George shouts "Please save me from the monsters". The Doctor is pulled into the cupboard with Alex.
In the house, Purcell runs up to Amy and Rory, asking for protection. Before they can react a wooden doll grabs him and he, too, becomes made of wood. Amy and Rory flee and hide in a room while the two dolls stand outside demanding to play. The Doctor and Alex arrive in the house. Alex wonders where they are but the Doctor tells him that they are in the doll's house in the wardrobe.
Amy is caught and made into a doll, too. Rory runs away from the dolls. The lights flicker in a group of five, which Alex recognises as George's thing. They are pursued by a doll, holding it off with a giant pair of scissors while the Doctor realises that George is a Tenza, an alien "cuckoo" that finds parents and gives them exactly what they want. He says that George has been made frightened, setting in motion all of these events subconsciously: he has to be made aware of what he is doing. As the Doctor and Alex back away from dolls onto some stairs they are joined by Rory doing the same thing in the opposite direction. The Doctor shouts to George to attract him to the wardrobe and the little boy appears in the house. The dolls surround George. The Doctor asks why George would be afraid. Alex explains that they needed help to deal with George's fears. The Doctor explains George thought he was being sent away. Alex runs down the stairs and hugs his son. He promises to never send him away. The dolls freeze.
The next morning, Mrs Rossiter wakes up in the bin bags, blaming her tablets. Amy and Rory step out of the lift. Purcell is lying on the carpet in his flat. Claire arrives home finds her son happy and playing with Alex and the Doctor. As the Doctor leaves, he tells Alex that George will grow up normal but he may return around puberty. Amy and Rory and the Doctor return to the TARDIS.
The display showing the time and place of the Doctor's death appears on the screen. The song that the wooden dolls sang ("Tick tock goes the clock") plays over the scene.