He staggered to his feet and fell down.

The faint sound of Thornton's voice came to them, and though they could not make out the words of it, they knew that he was in his extremity.

His master's voice acted on Buck like an electric shock, He sprang to his feet and ran up the bank ahead of the men to the point of his previous departure.
Again the rope was attached and he was launched, and again he struck out, but this time straight into the stream.

He had miscalculated once, but he would not be guilty of it a second time.

Hans paid out the rope, permitting no slack, while Pete kept it clear of coils.