"Hey, Pa!"
"Yes?"
"Come on! Look!"
"I'm coming! Hang on to your shirt!"
He drove to the foot of the knoll, looked in the direction Tad indicated, and knit his brows in wonder. Three hundred yards farther on, almost squarely in the center of the Trail, was another wagon. It was oddly still and only half real, a ghost that haunted the Trail. Its once taut canvas cover sagged, and the back flaps gaped emptily. Emma turned puzzled eyes on Joe.
"What do you think it is?"
"I don't know. Let's drive down and see."
As he drew nearer he knew that, though doubtless this wagon had once had a driver, it contained no people at all now. Tad, racing toward it, stopped uncertainly and waited while Mike bristled beside him. The youngster had been halted by sight of the oxen that had once drawn this wagon, but that now lay dead in their yokes. Joe stopped the mules, handed the reins to Emma, and walked slowly toward the wagon. His courage restored by his father's presence, Tad kept pace with him. Joe looked at the oxen, dead too long to have any hope of discovering what had killed them. He swung up to look into the wagon and, as he had expected, found it empty.
"What do you think happened?" Tad asked in awed tones.
"I don't know."