The episode picks up from the ending of The End of Time in which The Doctor has just regenerated and is crashing back towards Earth. After narrowly avoiding a collision with the Big Ben clock tower, the badly-damaged TARDIS crash lands on a shed in the back garden of the young Amelia Pond in Leadworth, a small village near Gloucester. Amelia takes him inside and helps him satisfy his strange food cravings (only being appeased with fish fingers and custard) before taking him upstairs to show him the scary crack in her bedroom wall. The Doctor discovers it is not just a crack in a wall, but a crack in time and space itself, and on the other side is a prison run by the Atraxi. The Atraxi deliver a warning to the two: “Prisoner Zero has escaped," but before the Doctor can help further he is interrupted by the TARDIS’s Cloister Bell: if not stabilised the engines will incinerate. The Doctor needs to pilot the TARDIS into the future to stop the engines from phasing. He promises Amelia he will return in five minutes, and leaves. She packs and begins to wait for him.
The Doctor returns and believes only five minutes has passed for Amelia. He runs out of the TARDIS, shouting that Prisoner Zero is in the house, only to be hit on the head with a cricket bat, rendering him unconscious. He wakes up to a female police calling for backup on her radio. He tries to get up, only to find the officer handcuffed him to a radiator, saying he was breaking and entering her house. The Doctor asks where Amelia is, and the policewoman tells him she has not lived in the house in six months. He then tells the policewoman to count how many rooms were on the floor of the house they are currently on; whilst she counts five, he counts six. The Doctor tells the officer to look at a door with the corner of her eye, and she realises she had never seen that door before - A whole room she had never even noticed, as it had a perception filter that made it unable to be noticed. Despite the Doctor's objections, the officer goes into the room, and finds the sonic screwdriver. She picks it up, but on her way out, Prisoner Zero, a serpent creature with the head of an anglerfish, appears behind her head. The Doctor shouts from outside the room not to look at it - once it knew the officer had seen it, it would kill her. The office then sees Zero and runs out of the room, handing the Doctor his screwdriver.
He locks the door, and then attempts to unlock the handcuffs, but the screwdriver malfunctions. The Doctor tells the policewoman to run, and that her backup will come to help. She reveals that there is no backup coming, and that she is not even a policewoman - she is a kissogram in costume, and that she had dressed up as she was worried when she heard the Doctor coming (She claims it was either this or a French maid). The door that Amy just ran out of suddenly falls forward, revealing a man and his dog. The officer asks how that is possible, but the Doctor points out that the man can only bark, not speak English - it was Prisoner Zero. The Doctor tries to convince Zero not to attack, but an announcement is suddenly made from somewhere outside: "Prisoner Zero will vacate the human residence, or the human residence will be incinerated". While Zero goes to a window to locate the source of the announcement, the Doctor manages to use the sonic screwdriver to free himself from the radiator, and he the the officer escape. Outside of the house, the Doctor notices a rebuilt shed, identical to the old his TARDIS destroyed when he landed on it the last time he was here. The Doctor smells (and tastes) the shed and deducts that it is twelve years old, meaning it had been twelve years since he had last seen Amelia. He asks the policewoman why she said it had only been six months, and she angrily replies, "Why did you say five minutes!?" in a Scottish accent, revealing this is the adult Amelia Pond. After a few minutes, they pass an ice-cream van that is playing the same announcement that they heard in the house. They look around, and every sound-emitting device is playing the same announcement. The Doctor realises that the 'human residence' is not Amelia's house - It's the Earth.
The Doctor deduces that they have twenty minutes before the Atraxi weapons power up, and therefore only that amount of time to save the world. However, he is unable to access the TARDIS while it is rebuilding itself, and the Sonic Screwdriver is destroyed when he uses it to try and attract the Atraxi. He also discovers that Amy has been creating dolls and drawing pictures of him since his crash twelve years ago. Prisoner Zero also mentions that it is not responsible for the crack in time, mocking the Doctor for his own lack of knowledge about its origin and telling him, "the pandorica is open, silence will fall". With others who know her thus convinced of his identity, he uses a resident's laptop and Rory's phone to transmit a computer virus around the world that sets all clocks and electronic displays to the number zero, therefore notifying the Atraxi of Prisoner Zero's presence and allowing them to track it to Leadworth as the source of the virus. He explains to Amy and Rory that the "Multiform," or Prisoner Zero, needs a dormant host and can change into the shape of whatever the host dreams of. Therefore, Prisoner Zero has eight disguises because of the eight comatose patients at the hospital. In a standoff in the coma ward of the hospital, Prisoner Zero attempts to steal Amy's dreams and memories to use as a disguise, having built up a psychic link with her from years of living in her spare bedroom and changes into the Doctor and Amy's childhood self. The Doctor prompts Amy to instead think of the undisguised Prisoner which she saw earlier at the house; thus, Prisoner Zero manifests as itself, and is recaptured. Before disappearing, Prisoner Zero repeats the warning, "silence will fall."
Angered by the fact that the Atraxi would attack Earth, the Doctor calls them back and dons his new outfit to have a meeting with them on the hospital's roof. He tells them that aliens have invaded before and to look up how they were defeated. The Atraxi discover who the Doctor is and promptly leave. The Doctor then returns to the TARDIS, which by this point has finished repairing itself. He leaves to perform test runs and then returns to Amy, though he is inadvertently two years late. He shows Amy the regenerated TARDIS (complete with a new sonic screwdriver), and she agrees to travel with him on the condition he returns her home for the next day, which unbeknownst to the Doctor is her wedding day.
* Matt Smith (Eleventh Doctor)
* Karen Gillan (Amy Pond)
* Arthur Darvill – Rory Williams
* Caitlin Blackwood – Amelia
* Nina Wadia – Dr Ramsden
* Marcello Magni – Barney Collins
* Perry Benson – Ice Cream Man
* Annette Crosbie – Mrs Angelo
* Tom Hopper – Jeff
* Arthur Cox – Mr Henderson
* Olivia Colman - Mother
* Eden Monteath – Child 1
* Merin Monteath – Child 2
* David de Keyser – Atraxi Voice
* William Wilde – Prisoner Zero Voice
* Patrick Moore – Himself
Writer Steven Moffat
Director Adam Smith
Script editor Lindsey Alford
Producer Tracie Simpson
Executive producer(s) Steven Moffat
Production code 1.1
Series 2010 series
Length 65 minutes
Originally broadcast 3 April 2010