The bathtub was still full of champagne when Peter Christian Barrie barged into the gamblers' hotel room just after dawn on Labor Day in 1926 with bad news to share.

The party had been rolling since Saturday at the Congress Hotel in downtown Chicago, and as the sun rose on Monday there were still some women over, and everyone was half-drunk. The gamblers, described enigmatically in the New York Daily News a decade later as "a railroad man and a local millionaire," were celebrating the $250,000 they planned to win that afternoon at Lincoln Fields, a new racetrack 30 miles south of the city.

Nothing is certain on the thoroughbred racetrack, but the men thought they had something as close to can't-lose as it gets. Their planned coup wasn't exactly on the level, but it wasn't exactly illegal either. It relied somewhat on the gullibility of the betting public, but mostly on the extraordinary talents of Barrie, the Scottish horseman who blew into their pre-race victory celebration with a warning that all was not well.

Barrie had red cheeks, black hair, and an indistinct sort of face that could pass as a stablehand's or a stockbroker's, depending on the exigencies of the particular con he was running at the moment. His antecedents were hazy: A veteran of the Battle of Gallipoli and Dartmoor Prison, he trailed alibis like ex-lovers.

He was a master, at 38, of the various measures a man could take to bend the odds at the track. He knew, for example, just how much heroin to shoot into a horse's neck to make him "think he was Pegasus," as the Daily News put it in 1932 (about 30 milligrams by hypodermic needle, or 160 milligrams down the throat).

But it was Barrie's fingernails that told the story of his particular genius: They were nearly gone, eaten away by the bleach and ammonia he rubbed into the hides of thoroughbred horses so that racetrack stewards, detectives, jockeys, and even the horse's own trainers mistook them for entirely different creatures.

The horse bleaching was in the service of an elegant scam that the gamblers called "ringing." You take two horses, one slow and one fast. The very slow one doesn't actually need to exist, but it's convenient if it does. You enter the slow horse in a race for slow horses, but on the day of the race, run the fast one instead. No one but you and the gangsters staking you know that the slow horse is really the fast one, so the horse goes off at long odds, and when he wins, you clean up.

The art of the con is in making the track stewards and the bettors believe the winner really was the slow horse having an inexplicably good day. That's where Barrie came in. He was a horse painter, perhaps the best in the world. His tools were simple: bleach, ammonia, bandages, silver nitrate, and henna in shades from blood to chocolate. He could turn a bay with a white star on its face into a dappled gray, and he could do it so convincingly that the gray's last trainer would swear it was his horse.

If the painter was really good — and Barrie was the best — it was hard to go wrong. But that Labor Day in 1926, when dawn broke over a muddy track at Lincoln Fields, Barrie realized he had a problem.

With $2,500 fronted by the two gamblers, who came from Minneapolis, Barrie had bought a quick horse named Kalakaua and a hundred-dollar stinker named Bobby Dean. He shipped both of them to Washington Park Race Track, a brand new track just outside Chicago, where he got to work. One of the Minneapolis gamblers sat outside the stable, whittling a stick and whistling. Inside, Barrie laid out his tools.

Kalakaua was a light bay. Bobby Dean was dark brown with a white star on his forehead. The alchemic process by which Barrie transformed Kalakaua into an ersatz Bobby Dean began mundanely enough, with a thorough shampooing, but soon Barrie would be boiling pots of exotic dyes imported from Germany, and the wash of strong chemicals would have overpowered the hay and manure smells of the racetrack stall.

Years later, Barrie described his technique in detail to a Daily News reporter. After shampooing the horse, he would put tape over its eyes for protection, then bleach its hair white. The strength of the bleach wash was vital: Too much would make the horse's skin contract and slow it down; too little would spoil the dye job, which Barrie accomplished with hot henna applied with his bare fingertips.

If the horse he was mimicking had white spots, Barrie would rebleach the corresponding bits of the ringer after the dyeing work was done. If the horse had a white face or markings on its brow, Barrie recreated them by applying stencils fashioned out of adhesive bandages. He used a rubber stamp to mimic a dappled horse's white spots; he colored a nose by smacking it with silver nitrate. He could cut an ear tendon, pluck tail hairs, or adjust a mane in pursuit of an identical match. If a stallion was running as a gelding, Barrie would apply blocks of ice to its testicles just before the post parade to make them disappear. Then there was work inside the horse's mouth, the details that sold the whole ruse. A 3-year-old running as a 2-year-old would need its teeth adjusted, accomplished with a knife and a drill and all the skills of a veterinary dentist, which Barrie claimed to have been before the war.

All this took time, and it had to be done in perfect solitude. That day at Washington Park, as Barrie transformed Kalakaua into Bobby Dean, the Minneapolis gambler serving as the lookout would whistle louder if someone passed nearby, and Barrie would cover his work in progress with a blanket until the whistling quieted and he could get on with his painting.

After Barrie laid down his tools, Kalakaua's forehead now bleached with Bobby Dean's white star, he packed the slow horse into a cattle truck and shipped him off to Ohio. Then he drove Kalakaua to Lincoln Fields for the race. The gamblers rented their room at the Congress and loaded up on champagne. All was in place for an elegant scam.

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