Chattering to Tomas about the 18th Century Enlightenment, you fail to notice any spark of interest in his eyes. As your banter winds along, though, Tomas seems to notice that he's being spoken to.
He peers into your eyes with great interest. You continue happily, and he leans closer and closer, peering ever more deeply.
Suddenly you realize he's admiring his own reflection. You throw up your hands, figuratively speaking, and try a new tactic, something a bit more desperate.