He must find out what lay behind that mound of earth.
Suddenly a curious sound fell on his ears.

It was so faint that at first he doubted the evidence of his senses.

Then as the wind fell it came louder.

It was exactly like some hollow piece of metal being struck by a stick, musical and oddly resonant.
He concluded it was the wind blowing a branch of a tree against an old boiler in the ruin before him.

The trouble was that there was scarcely enough wind now for that in this sheltered cup.
But as he listened he caught the note again.