The Doctor Arrives

The TARDIS materialises on Earth, in a park in Colchester, rather than the intended destination of the Fifth Moon of Sinda Callista. As The Doctor steps outside he is thrown to the ground. He is then shocked to see the TARDIS dematerialises with his travelling companion, Amy Pond, still inside leaving him behind.

The following day, outside a nearby house, passers-by are seen being lured into the house by a voice seeking help, from the intercom at its front door. When the door opens they are encouraged to ascend the staircase to the first floor. But as they enter the room flashing lights are seen and screams are heard emanating from behind the now closed upstairs door.

Meanwhile, in the downstairs flat a man called Craig and his female friend, Sophie, discuss a strange stain, which is on the ceiling in the corner of the room, and their plans for the evening. Their plans, however, are curtailed when Sophie has to leave so that she can tend to another friend who is upset over a recent break up. This leaves Craig with the prospect of spending the evening alone. However, when the doorbell rings he is delighted as he thinks it is Sophie returning. But when he opens the front door Craig is shocked to discover it is The Doctor who claims to have seen an advertisement to rent Craig’s spare room.

Craig

Before he can be stopped The Doctor walks in and gives Craig a paper bag containing a large amount of money as rent. The Doctor explores the downstairs flat and, so as to persuade Craig that he will be a good lodger, he cooks Craig an omelette. On noticing the stain on the ceiling he warns Craig to avoid touching the rot. Claiming to be an expert in rot he tells Craig that he will fix it himself. This convinces Craig to allow The Doctor to stay. Then in his room The Doctor contacts Amy, using a communication device in his ear, to discuss what is going wrong. The TARDIS then begins shaking violently and The Doctor tells Amy how to fix it. Unknown to The Doctor another passer-by has been enticed inside the house and upstairs.

The next day, while The Doctor is showering, Craig hears a loud bang from upstairs and so goes upstairs to investigate. The Doctor panics and fears Craig is in danger, so grabs Craig's toothbrush in mistake of his sonic screwdriver. The Doctor finds Craig safe and is introduced to Sophie who has just arrived and let herself into the flat. After receiving a phone call Craig asks The Doctor to join him in his pub football league as his team lacks a player. Believing football is played with the sticks The Doctor agrees.

Sophie

At the football match, The Doctor at first shows how unfamiliar he is with the game but he soon shows his skill and talent scoring many goals so winning the match. Craig, however, becomes jealous of the increasingly popular Doctor. However, while celebrating their win The Doctor witnesses Craig and his friends becoming stuck in a time-loop. At the same time the TARDIS shakes violently and, back at Craig’s house another person enters the upstairs flat. The affects on the TARDIS concerns The Doctor who is worried that Amy could be lost in the TARDIS forever.

Back at the flat, Craig asks The Doctor to keep out of his way while he is with Sophie so he can profess his love for her. The Doctor however interrupts them and as they talk he convinces Sophie that she can do anything and encourages her to work with Orang-utans like she dreams. Later that night, after Sophie has left, Craig touches the rot, that is spreading even further over the ceiling, only to pull his hand back in pain.

In the morning, The Doctor prepares breakfast for Craig only to find him nearly dead. The Doctor makes him remedy out of teabags for Craig to drink. Craig claims there is a business meeting he needs to go to but The Doctor insists that he stays in bed to rest. Suddenly Craig wakes up to find that it is now the afternoon. He rushes to work to find The Doctor at his desk insulting a rude client. His manager then says he was useful at the meeting. This upsets Craig who becomes jealous of The Doctor for being better than him and for suggesting to Sophie that she should leave to fulfil her dreams. Craig is worried he could lose Sophie - the woman he secretly loves.

The Lodger

Aware that the first floor room may not be all it appears to be, and with increasingly frequent time-loop events occurring, The Doctor builds, in his room, a scanning device in an attempt to discover the nature of the threat. Craig however, discovers The Doctor’s apparatus forcing The Doctor, so he can remain in the house, to mind-meld with Craig. This informs Craig of The Doctor’s alien nature. Sophie then arrives at the house and spots a young girl at the top of the stairs. She asks Sophie to help her and so Sophie follows her into the upstairs room. After seeing her keys in the door The Doctor and Craig become aware of Sophie’s arrival. Then, on hearing a scream, they race up the stairs to save her. The Doctor contacts Amy who reveals to him that according to the house’s blueprints, which she has discovered in the TARDIS’ databanks, the building is only one storey tall and so there is only the ground floor. When they open the upstairs door The Doctor and Craig discover they have entered a spaceship. The Doctor, however, is more shocked to discover that the inside of the spaceship resembles the Console Room of a TARDIS.

They also discover Sophie being pulled towards a console. The Doctor rushes over to her and, with the help of Craig, they manage to break the contact between her and the console. A man then appears which The Doctor realises is a holographic auto pilot who is able to appear in the form of the various victims it has attracted, as well as Craig's seldom-seen neighbour. The Doctor learns from the hologram that the spaceship crashed killing all the crew. Since then the auto pilot has rebuilt the spaceship and, so as to find a suitable replacement, it has been luring in humans so they can be tested. However, all the human minds tested so far have proved not sufficient for the task so killing them. Recognising The Doctor as a suitable pilot, the ship tries to pull him in. Knowing he cannot pilot the ship safely (as it would destroy the entire solar system in the process), The Doctor realises that the spaceship had only lured in people who wanted to escape or leave somewhere, hence why it hadn't attempted to lure Craig before (nor Sophie, until The Doctor motivated her to better herself). After finally admitting their love for each other, both Craig and Sophie touch the panel’s activator, causing the spaceship’s engines to shut down and the spaceship to implode. Fleeing, the house they notice the spaceship vanish along with the entire top floor which, The Doctor explains no one else has noticed due to a perception filter.

With the danger over, and the TARDIS able to materialise, The Doctor says his goodbyes to Craig and Sophie. Back in the TARDIS The Doctor is reunited with Amy and they travel back in time a week so that Amy can leave the note in the newsagent’s that directed him to Craig’s flat in the first place. However, when Amy looks for a red pen with, which to write the note, she looks inside the pocket of The Doctor’s discarded jacket that is draped over a chair. Instead she finds the engagement ring that Rory had given to her before he was erased from time. Its presence unsettles her. Unbeknown to both The Doctor and Amy back in Craig’s flat, in the wall behind Craig's fridge, another crack in the universe glows ominous as it grows larger…