His face here, when you accept to have sex with him for the second time. His gaze mostly.
It has always troubled me.
The way he looks away while saying “until morning at least”.
I can see several reasons:
1 – He’s not really into it and doesn’t exactly want to have sex.
2 – He wants it but feels quite awkward because he begins to have feelings for the PC and feels bad about manipulating them.
3 – He’s said this countless of times before to his “targets”, and they didn’t survive until morning since Cazador would ultimately take them.
4 – A part of him doesn’t want it to stop in the morning, but he’s not ready yet to face his growing feelings for the PC.
5 - He's just tired of the performance, of pretending.
And I’d tend to believe that it could be a little bit of all of this, to a certain extent.
In any case, it’s one of the rare act 1 moments when his mask briefly falls and reveals doubts/vulnerability. And IMO he doesn’t even realize it himself.
Look how quickly and easily he composes himself right after it. As if his doubts suddenly disappeared.
The smile and grandiloquent declaration are back, the mask is back.
It’s an automatism. The 'well-presented' face that opens a lot of doors is so engrained in him that he instinctively adopts it, not only to lure others, but also himself.
But for those few precious seconds, he let himself be seen, without even knowing.