The first thing he feels is a surge of emotions, and an impulse to likewise mash his face against the scientist's as gracefully as he can manage. It's not a bad attempt. He's kissed before, and passionately, too.

Then, after a couple of seconds, the implications of Wilson's pleasantly fresh breath hit him.

He planned this. I played right into his hands. Just like before, he had me in checkmate before I thought we'd even really begun to play. This causes an upwelling of irritation, admiration, and spite in his twisted soul.

Next, he takes notice of Wilson's hair, as he instinctively runs his fingers through the scientifically magnificent coiffure, dark and soft as always, and he finds himself thinking back to a certain someone else's hair, dark and soft against the pillows while the smell of roses tickles his nose gently.

And then the guilt hits him. Not because he has any moral qualms about kissing a man, no, but because he's kissing anyone at all that isn't her.

I can't spend my whole life lingering on thoughts of Charlie.

Can't you, though? Shouldn't you? When you're the one who destroyed her?

This... was not where he was hoping this would go. He doesn't pull away from Wilson, but it's clear from his fading enthusiasm that he isn't as into it as he was a moment ago.