"A secret's worth depends on the people from whom it must be kept."
― Carlos Ruiz Zafón, The Shadow of the Wind
He's never told Clara about River. Oh, he's mentioned Professor Song once or twice, alluding to past adventures, but he hasn't so much as whispered a word about River Song, his wife.
Secrets protect us. Secrets keep us safe.She'd always kept secrets from him-it was her damn catchphrase, after all: spoilers. Now it was his turn.
No, it wasn't revenge. He wants to tell Clara about his brilliant wife, about how she trusts him so much she'll jump off buildings knowing he'll catch her, how she leaves him messages through all time and space, how he trusts her with everything, even his name.
But he hasn't seen River in a very long time, not since Manhattan. He wonders if their timeline has been rewritten, if she somehow went to the Library and Darillium never happened. Or maybe she doesn't love him after all, maybe she never loved him, and it was all just a game so she could be close to her parents.
He hates himself for thinking that way, for doubting her, but it's no more than he deserves. Even so, he can't bring himself to speak of River to anyone, not even Clara. River is all he has now, the only water in his forest, and he doesn't want to spill a drop.