Corner of the Eye (short story)

Summary
Tom and Kathy are chatting on instant messenger and Tom recounts -- for the fiftieth time, as Kathy keeps forgetting -- how, one day he noticed a short, bald man standing behind him in the mirror. Looking through some old photos, he finds the same man behind him in all of them. He decides to post a "have you seen this man?" ad.

The Doctor appears, having read the ad and arrived at Tom's house before it was posted, to question him. Tom reveals he has had agoraphobia for the last ten years, which the Doctor remarks as being odd. Tom shows the Doctor his computer, explaining he speaks to Kathy via instant messenger and the Doctor asks why they do not live together; they seem to have split up ten years ago. Tom cannot think of an answer.

The Doctor asks if Tom has any other form of contact with anyone. Tom replies that he doesn't write letters, he hates the phone and he cannot email since he doesn't even have an internet connection. After repeating this a few times, Tom realises that Instant Messenger requires an internet connection, so he really shouldn't be able to chat with Kathy. The Doctor searches the house, and discovers Kathy in the cellar, underneath old wine racks, looking as if she has been there for ten years.

The Doctor tells Tom about Floofs, short, hairless creatures like the one in all Tom's photos, who hide out of people's sight, disorganising their lives by moving keys around, stealing important letters and so forth. Tom's Floof killed Kathy and set up a computer programme to write on instant messenger just as she would. The Floof messed around with Tom's head, removing his suspicions and confining him to his house to cut him off from the rest of the world. The Doctor orders the Floof to stay still so they can talk, and explains that he is taking Tom away so that the Floof cannot harm him any more.

The Kathy programme asks Tom how he can be chatting now if he left the computer. He tells her he is not the real Tom. On his instructions, she asks him where he is. He answers with the same list of information she gave him earlier, indicating that he is now just a computer programme too.

Characters

 * The Doctor
 * Tom
 * Kathy
 * Floof

Continuity
As Rose does not join the Tenth Doctor on this adventure it could take place around the time of Attack of the Graske, between the penultimate and final scenes of Doomsday, or somewhere between The Runaway Bride and Smith and Jones.