"Oh."

He gives Robin back some space, but only enough bring up a sleeve to wipe at his eyes with. And those sleeves are made of leather, so mostly just smears it all evenly around his eyelids instead of welling along the rims.

And it's somewhere in this that he finally notices that something is wrong, and hesitates.

He suddenly leans in again and goes to give Robin's face and neck a much more thorough sniffing, along with a thoughtful "Hmmm..."