My body is reacting to physical stimulus. Pain. It means nothing.

[Sherlock is such a good liar that to anyone else it might seem the truth. He goes back to mulling this little puzzle over.]

It's not something so banal as -- [his concentration briefly breaks and he sucks in a breath through his teeth] -- consummating our feelings or trust or any of that rubbish. You're hardly that sentimental.

[But this is still different from her doing it to anyone else, at least to her. He's still mulling it over, as if he's working out the solution to a case.]

It's not just about what you can take, it's not just about your own pleasure--and you do certainly enjoy this while working or at play--it's about something else. Something-- [Another wince. It's getting harder to concentrate.]

You think you'll get something from me that no one else ever has, that's more than I've already given you.

[The look he flashes her is pure defiance.]

You're wrong.

[That defiance is completely ruined by the way he lets out a grunt, despite himself, right after he says it.]