In Kamala Harris’s big general-election debate four years ago, she faced off against an opponent with a fly on his head.

In her immeasurably bigger debate on Tuesday night, she confronted an opponent with bats inside his.

And out they came, flapping and screeching, when he brought up cats and dogs.

He was talking about what he couldn’t stop talking about — the millions of migrants who, he insisted, were depraved criminals being dumped on us by cackling foreign leaders — and in his indiscriminate zest to describe an American hellscape, he repeated debunked stories that in Springfield, Ohio, these desperate newcomers were noshing on Fido and Whiskers.

“They’re eating the dogs. The people that came in — they’re eating the cats. They’re eating the pets of the people that live there,” he sputtered, red-faced. Harris didn’t even have to correct him, because David Muir, one of the two ABC News anchors moderating the debate, got there first and did it for her.

Some dark fantasies need immediate dispelling. And some deranged fantasists need to be tugged back into reality before they wander so far from it that there’s no returning.

Trump made a raving, rambling fool of himself on Tuesday night, and while Harris by no means did everything right, she had the good sense to alternately call him out on that and simply watch him unravel. She had the discipline to shake her head sadly and smile dismissively when he made laughably false accusations against her. She had the skill — here, on full display, was the prosecutor in her — to needle him into maximal seething.