"And that is the mystery?" asked Tad.
"Yes."
"It is the strangest story I ever heard," said the boy quietly.
"What I was about to say, is that the herd will go on without me. Colonel McClure is sending his own foreman through with it instead. Ruth and I are to be married at once, and we shall go to my little ranch in Montana."
In view of the fact that Stallings was severing his connection with the herd, Professor Zepplin decided to do likewise.
Next morning, at sunrise, Bob Stallings, with Miss Ruth, by his side, both radiantly happy, rode out to the camp. The Pony Rider Boys had packed their kits and loaded their belongings on their ponies. Regretfully they bade good-bye to the cowmen.
Tad's parting with Big-foot was most trying. In the short time they had been together, a strong affection had grown up between the two. The plainsman had been quick to perceive Tad's manly qualities, and the boy, in his turn, had been won by the big, generous nature of the man. They parted, each vowing that they must see each other again.
As the great herd moved slowly northward, three cheers were proposed for Bob Stallings and Miss Brayton. This the cowboys gave with a will, adding a tiger for the Pony Rider Boys.
The trail wagon, pulling out at the same time, held a grinning Chinaman, huddled in the rear.
"Good-bye, Pong!" shouted the lads.