Suddenly a cry from Matt Boyle called the others to him.
"What is it?" asked Mr. Thornton.
"Here's where a strange pony has been tethered," was the answer. "See, those shoes are none of ours," and he pointed to the hoof-marks in the soft ground.
"That's right," admitted Mr. Thornton. "And here's where a man has come along and mounted him," he went on. "I see it now. That fellow rode up here, and picketed out his horse. Then the storm came and he was hurt. He thought he saw a chance to get that paper and he took it. He waited until we were all asleep and took it out of my desk. Then he sneaked out, got his horse, and rode off."
"That's it!" cried Billy.
"On the trail, boys!" shouted the ranchman. "I'll give a hundred dollars to the one who first sights that fellow!"
"Whoop-ee!" yelled the cowboys, flinging their hats in the air. One or two fired off their big revolvers, and several swung their lariats. Then, amid shouts and yells, and with a clatter of hoofs, the cavalcade started off on the chase.
"We'll stick together!" called Billy, to his two chums.
"Oh! I hope we can get that fellow!" cried Frank.
"If we don't find him in this direction I know where we ought to look for him," said Andy, for the trail was leading toward town.