Suddenly, at a turn in the path, his eye caught a sight which made him throw his horse back on his tracks. A sheer precipice fell away a thousand feet below him, and beetling cliffs cut off the sky above. Across the path trickled a little stream. And there in the stream, so clear they could not be misread, were the marks cut by a horse's feet sliding over the precipice.
The policeman dismounted carefully. There was scarcely room for him to pass his horse on the narrow ledge. Where the stream had worn it it sloped downwards at an uncomfortable angle. He knelt beside it and traced the marks of the shoe-calks with his finger. They led over the edge. Eighteen inches down the mountain side was a fresh scar where steel had struck a projecting corner of rock.
A thousand feet below the green water slid and swirled in the bed of the canyon.