A Twitch Upon The Thread

Title: A Twitch Upon The Thread
Character(s): The Tenth Doctor
Pairing(s): Ten/Rose
Rating: U
Timeline: School Reunion
A/N: The title, and the text of my LJ cut, both come from the book Brideshead Revisited by Evelyn Waugh. (I'm told that the quotes both come from the Father Brown books by Chesterton, but I found them in Brideshead.)
Disclaimer: Characters you recognise belong to the BBC.
Summary: Why the Doctor will never voluntarily leave Rose behind.

( '... an invisible line ... long enough to let him wander to the ends of the world and still bring him back with a twitch upon the thread' )