"Don't know about that, sir; I feel all of a tremble."

"Then fire anywhere, as long as you don't wing me. I want you to prop yourself between these two rocks and keep as quiet as you possibly can. Don't let yourself be seen. I'll take your chum's rifle. If you hear me fire, hop across the line as sharp as you can, with your bayonet at the charge. Buck up, man, and keep your nerves."

Having seen the sentry take up the position indicated—in a niche formed by two large boulders in the side of the cutting—Terence secured the rifle and bayonet of the dead man. The rifle was a magazineless '303, with Martini action, similar to those issued to troops engaged in home defence.

Donning the pouches of the unfortunate sentry, the lieutenant took out a cartridge, inserted it into the breech and closed the breech-block. Then, having ascertained by touch that the back-sight was down, he crossed the line and commenced to walk the murdered sentry's beat.

In the darkness his naval cap and great-coat were not to be distinguished from those of the man he was impersonating. He felt certain that should the crime have been committed by a German agent, the reason was the destruction of the tunnel. When the mail train stopped, the miscreant would certainly betake himself to a safe distance; but with his work uncompleted, he would almost certainly return. He had marked the time when the two sentries were posted he knew when their reliefs were expected. Before that time he must render the second sentry incapable of raising an alarm and then proceed with the blocking of the line.

In his operations the spy had made one serious blunder. He had shot the sentry, as had been surmised, and had thrown his body on the line in front of the goods train, so that it would be taken for granted that the luckless man had been knocked down while incautiously walking his beat. But instead of the train mangling the victim's body and thus destroying all traces of the fatal shot, the wheels had only severed one of the unfortunate man's feet.

For half an hour Terence maintained his sentry-go. The rain was now falling heavily. His great-coat felt as weighty as lead. The moisture dropped from the peak of his cap and filled the palm of his left hand as he held the butt of his rifle.

The sub.'s nerves were in splendid condition. The hand that held the rifle was as steady as a rock. With eyes and ears strained he paced to and fro, prepared at the least sound to face about, bring his rifle to the ready and fire.

From a strategic point of view his position was an unsound one. By the remaining sentry's description the miscreant must have retired from the scene of action not by running into the tunnel but by scaling the fairly accessible wall of rock. Consequently the anticipated attack would be from that direction, and Terence was liable to be fired at from a height of from ten to fifty feet above his head.

Presently a dull but increasing rumble greeted his ears. It was a local down-train, which had just entered the far end of the tunnel. Instead of grounding the butt of his rifle and facing the line, as he had seen other sentries do, the lieutenant marched to the mouth of the tunnel; then, leaning his shoulder hard against the massive stone buttress, waited for the train to pass.