A few months ago, I decided to conduct an experiment: I plopped a video camera in the middle of my living room and left it running after I left the house so that I could see what my dog does when he’s home by himself. My finding was that he doesn’t do much: looks around inscrutably for a while, whines half-heartedly, then goes to sleep on the couch.

Wouldn’t it be great if we could run the same test on Donald Trump? The guy lives to be seen, after all. He is a public-facing animal whose every utterance, gesture, and glance is performed for the eyes of others. To imagine Trump existing alone—Trump brushing his teeth in front of the bathroom mirror, Trump taking a solitary jog, Trump on a solo stroll through the Metropolitan Museum of Art—is to wonder what thoughts enter his head when he has no reason or excuse to say them out loud, what faces he makes in response to external stimuli when there’s no one around to wonder what he’s feeling or thinking. The mystery is not whether he makes a sound when there’s no one around to hear him, but what becomes of all his anger, resentment, and pettiness when the only target in his vicinity is himself.

Thanks to Chris Cillizza of the Washington Post, who captured a revelatory GIF of Trump at the very end of Wednesday night’s debate, we have something approaching a glimpse into the darkness. As you can see below, the clip shows Trump waiting at his podium while his hated opponent, Hillary Clinton, walks over to thank debate moderator Chris Wallace. It was clear what Trump was doing in this moment: Having resolved not to shake Clinton’s hand, he was trying to time his exit from the stage such that he wouldn’t run into her. This left him with a few seconds to kill, and kill them he did:

Look at those teeth. The downturned lips. The clenching of his jaw and the rage in his stubby fingers as he rips that piece of paper out of his legal pad.

It’s the image of a man who knows he has fucked it all up yet again—a man who cannot escape himself, whose body is fighting to blow itself apart. Yes, he is on television and he knows people are watching, but for once he appears to be incapable of caring. This is Trump distilled to the bitter despair that is the essence of his perverted version of charisma: the embodiment of deluded ambition finally exhausted once and for all, the human form of the word goddammit.

The moment he straightens up and steels himself is the perfect end to this very short story. The eyebrows go up, the head cocks to the right, and the shoulders square. But it doesn’t last. As Hillary Clinton glides in front of him, Trump can’t do anything but look down. Bad dog.

Read more Slate coverage of the 2016 campaign.