The horses knew first. Terry Thompson kept dozens of them on his farm just west of Zanesville, Ohio, a suffering river town and the seat of Muskingum County. Most of the living things in Zanesville had been born in Zanesville, or in the county at least; Thompson was one of the few importers. He had a particular eye for the unwanted. His horses weren't pretty animals except that they were horses: worn-out chestnuts, muddy grays, a semihandsome paint named Joe. There was even a donkey and a fat little pit pony in the mix, and now they were together in the pasture, more tightly packed than usual, running in a wide circle. They were rolling almost, the bunch of them moving slowly at first and now finding their old legs, picking up speed like starlings, like the bands of a hurricane.

A neighbor, a sixty-four-year-old retired schoolteacher named Sam Kopchak, first saw Thompson's horses sprinting around their hilly pasture, just on the other side of the wire fence that ran between their properties. Kopchak was on his way up the slope from the little white house he shares with his eighty-four-year-old mother, Dolores, to retrieve his own horse, a pinto named Red, from his small field out back. It was fifteen or twenty minutes before five o'clock, two hours before dark, and Kopchak wanted to bring Red into his barn for the night. He was a new horse owner, and Red was his only horse — that late Tuesday afternoon, October 18, 2011, marked only their ninth day of shared company — but he knew enough about horses to know that they don't normally run in circles, not by the dozens, around and around. There was a bad storm blowing in, but bad storms had blown into Zanesville before, and the horses had never torn after one another like that, kicking up the earth.

Kopchak was distracted from the horses when the grass moved nearby. He caught sight of a cat just then, a wildish male tabby named Klinger that had suddenly jumped out of the trees. Klinger hadn't made an appearanc...