At the same time, he heard the raucous gabbling of several voices.

Though his near-sighted eyes did not yet show the intruders to him, yet scent and sound made it ridiculously easy for him to trace them.
From early puppyhood, Lad had been the official guardian of the Place.
He knew the limits of its thirty acres; from lake to highroad; from boundary fence to boundary fence.

He knew, too, that visitors must not be molested as long as they were on the driveway; but that no stranger might be allowed to cross the land, by any other route; or to trespass on lawn or oak-grove.
And now, apparently, strangers were holding some sort of unlicensed revelry, down on the point.

His sense of smell told him that neither the Master nor anyone else belonging to the Place was with them.

True watchdog indignation swelled up in Lad's heart.