Nothing moving was in sight.

Suddenly, just as they cleared the bridge, and began to mount the opposite grade, there came a sharp report, sounding so close at hand the chauffeur clamped on his brake, and glanced anxiously over the side of the car.
"Blow-out, wasn't it, sir ?" "No," said West shortly, staring himself out into the thicket of trees at their left.

"It was a shot fired over there; a revolver I should say.
Wait a second, Sanders, until I see what has happened." It was largely curiosity which led him to leave the car.

The very conviction that it was a revolver which had been discharged brought a desire to learn the cause of the shot.

The sound of either a rifle or a shot-gun in that lonely spot would have been instantly dismissed as natural enough, but a pistol was different.