Winning is everything — and nothing.
Losing is nothing — and everything.
All that matters is the game.
The Players have decided on an Endgame. Play ends only when one side has been annihilated — even if the entire planet is destroyed in the process. They weren't expecting the Doctor to be one of the pieces — and neither was he. He really doesn't want to get involved.

The Doctor doesn't know who he is — but he's fast ceasing to care. Caught up in ennui, nothing seems to matter to him any more. He has no interest in the Cold War, in spies or double agents or secret documents.

But he's soon forced to take an active role. Because as far as the authorities are concerned, the Doctor is the Third Man...