Constant Companion (short story)

Summary
The Doctor, Jamie and Zoë visit a strange world where spring, summer and autumn all seem to be occurring at once. There, just outside the TARDIS, the Doctor finds a cat-like creature which he impulsively decides to take aboard the TARDIS and name Marmaduke. After some weeks of having the cat claw up the TARDIS corridors and shred the clothing in the wardrobe, the Doctor begins to suffer telepathic fits and finds that he can’t keep Jamie and Zoë’s thoughts out of his head. Concluding that Marmaduke must be responsible, he tries various methods of getting rid of it, but the cat always comes back -- and the world where he first found it seems to have disappeared. Realising the truth, the Doctor re-sets the co-ordinates and materialises on the cat’s homeworld several centuries in its future. The “planet” is in fact a pocket dimension inhabited by a powerful telepath who was exiled from her own people; the cat is an extension of her id which she created as a companion, but it became too much for her to handle. When the Doctor arrived she influenced him to take it away, but since the cat is a part of her mind, her powers have waned without it, and the Doctor simply had to travel into the future until she was no longer able to shield the planet from his view. The woman accepts the cat back with good grace, admitting that she was lonely without it... and as the Doctor departs, he realises that he will be somewhat lonely without it as well

Characters

 * Second Doctor
 * Jamie
 * Zoe

Continuity
to be added