Psi laughs, amused that so long after seeing Childermass strange has up to him asking about the very same "not friend" in question. There clearly had to be something going on between these two, but Psi can't ask about it now. Strange said dare first, not truth, so the relationship question would have to wait, if only for a moment.

So he tries to think up some kind of dare. Even if Psi did have something awful in mind he wouldn't use it on the first dare! Instead he just taps his chin thoughtfully while he thinks of what to say.

"I dare you to kiss the next person you see." he says, smirking as though he's just given out the best dare in the world.