[Narvin curled his lip back in an expression that was part snarl, part sneer.]

Because I'm sure that your concern for the humans will distract you to the point of it being useless to try to get anything out of you, I'll assist you with the Zygons for now. [His voice was soft, with a slight hiss to his words.]

And afterwards you'll owe me an explanation. If you refuse to give it willingly, I'll simply have to resort to other methods. I'm sure you're familiar with the mind probe. [Not that he has access to one these days, but he's hoping that the Doctor doesn't know that.]