In the summer of 1965, a female Dalmatian was stolen from a farm in Pennsylvania. Her story changed America.

Everyone in town knew Jack and his big, green pickup truck, with the wood-framed animal cab loaded on the back. When he was in the area, he'd stop in at Sponsler's Superette every few days to pick up meat scraps for the animals. Jack would come and go, disappearing one day and returning later in the week with 10 or 15 dogs in tow.

There was talk among the locals that Jack wasn't just picking up strays, that he'd steal dogs out of people's backyards and sell them off to medical labs in Philadelphia. But the county dog law enforcement officer—Fred Sponsler, who owned the Superette where Jack did his shopping—appears not to have filed any charges. Later on, Terry Clark and his sister Kay would conclude that their granddad had been carting live cargo to research labs in Harrisburg.

Jack's friends and fellow dealers would converge on his property every weekend to trade horses, goats, cats, and dogs while their children played on the ponies out back. It's impossible to know whether Jack Clark made a dogcatching expedition up to Slatington in June of 1965, but, one way or another, Pepper seems to have ended up at his weekly swap in Black Valley, on Sunday, June 27, five days after she disappeared.

By Tuesday, June 29, one week after her disappearance, Pepper was in the hands of Jack's good friend Bill Miller.

If you lived in Slatington, or Allentown, or just about anywhere in the region, the summer of 1965 would have been long and miserable. A four-year drought, made worse by a run of scorching, cloudless days, pushed New York City's reservoirs to half-capacity. Golf courses dried up, the rhododendrons and azaleas crumpled at the city's botanical gardens, trains and buses went unwashed, and the mayor proposed tapping the Hudson River for drinking water.

In all that nasty summer, no single day was more vile than June 29. The temperature reached 95 degrees in the afternoon, the humidity 50 percent. The New YorkTimes pronounced that an "asphalt-softening, brain-fogging heat" had overtaken the city. And somewhere on the 170-mile stretch of Route 78 that runs from Harrisburg, Pa., to the New York state border, 18 dogs—including two boxers, a Weimaraner, several mixed collies, and a pair of female Dalmatians, one of them Pepper—were locked in a small enclosure on the back of Bill Miller's pickup truck, crammed inside with a pair of goats.

Bill Miller ran Broken Arrow Kennels out of McConnellsburg, a half-hour's drive east from Jack Clark's place in Black Valley. Like the other dealers in Clark's circle, Bill was an older guy—and a regular target for Humane Society investigators. In February 1964, Dale Hylton had visited his farm in the guise of a buyer for a Long Island hospital, successfully placing an order for 170 research dogs. The unsanitary conditions he found there were grounds for a search warrant, and he later returned with a constable to file charges of cruelty to animals.

Miller would have another run-in with the authorities at the end of June 1965. He seems to have set off from McConnellsburg on Tuesday afternoon, a week after Pepper disappeared from the Lakavage farm, and made his way across the Susquehanna River on Interstate 81. From there he would have had a straight shot through Allentown and into New Jersey. But a few hours later, with Miller just moments away from crossing the New Jersey border, the local police in Easton pulled his truck off the road and asked to look in the back.

Distressed by the sight of 20 animals huddled in a cab with little ventilation, the cops wrote out a pair of tickets—$74 for overloading the vehicle and $10 more for "cruelty in transport"—and handed over the dogs and goats to the county animal shelter. Miller said he was on the way to Arthur Nersesian's research holding facility in High Falls, N.Y., and that he'd be back the next day to pick up his haul with a bigger truck. The shelter's proprietors agreed to release the animals if and when Miller could deliver the proper bills of sale. They photographed the dogs that night.