As the two young army engineers turned away from where they were standing to look up and down the gully which had been crossed at the time they had seen the last of their chum, they noticed that the cloud of poisonous gas was growing more dense. On every side the water-laden wood showed a thick and sickly yellow haze, the very appearance of which was enough to make one shudder.

For the time being the rain had let up. Overhead the heavy clouds were passing swiftly to the southward, but the wind seemed to be too high up to drive the poisonous gas away.

Dave and his chum traveled all of a quarter of a mile down the gully without getting any trace of Roger. Then they came back on the far side of the gully and progressed in the opposite direction.

This upper section of the wood had been under fire several times during the war, and was consequently much torn up. Shell-holes were to be met at every little distance, and here and there the dying trees lay across the underbrush.

Presently Dave clutched his chum by the arm and pointed to an opening leading down into the gully at a point which so far had not been explored. There on the ground lay a newspaper—a copy of the Stars and Stripes, the official sheet of the American Expeditionary Force in France. Both of the young civil engineers were much interested in the discovery of this newspaper, for they remembered that Roger had had a copy of the publication with him on their last trip forward. In fact, the senator’s son had read some articles aloud for the benefit of his friends.

“If this is the newspaper he was carrying, he must have come this way,” was Dave’s reasoning, and Phil was of a similar mind.

With caution, for the going was treacherous, the two young engineers made their way down the rocks and over the muddy places and through the rain-soaked underbrush toward the bottom of the gully, which, at this point, was thirty or forty feet in depth and probably twice that in width at the top. At the bottom was a tiny watercourse, gurgling over and around the jagged rocks.

Reaching the watercourse, Dave and Phil looked up and down for some trace of their missing chum. But on account of the poisonous haze, which filled the gully, it was difficult to see any considerable distance.

Dave motioned to his chum that he was going farther up the gully, and Phil nodded to show that he was willing to continue the search, even though the poisonous gas in that hollow might be highly dangerous for both of them.

They had progressed less than a hundred feet when, on coming to a momentary halt, they suddenly found several small stones rolling toward them from one side of the gully. Looking up in that direction, they discovered Roger seated on a rock and motioning to them.

The lost young engineer had his gas mask adjusted, for which both Dave and Phil were thankful. But he sat on the rock nursing his left ankle, and now they saw that he had removed his shoe and had the ankle bound with a bandage.

By looking up behind Roger it was easy to make out what had happened to him. In trying to make his way out of the gully after coming down from the other side, he had trusted his weight to some bushes near the top. They had given way, and he had come down almost to the bottom with a rush, falling and rolling over some sharp rocks as he did so. Then he showed them how his left foot had become caught between two of the rocks, and this had twisted his ankle, making it so painful that he could not use the foot.

Dave felt that the first thing for him and Phil to do was to get Roger out of the gas-choked gully. The young engineers had had not a little experience in carrying wounded men, and now this helped them to lift Roger and move him without causing the hurt ankle much additional pain. They did not attempt to get to the top of the gully at that point, but walked along the watercourse for several hundred feet, until they reached a point where egress from the hollow was comparatively easy. On the upper level all were glad to notice that the gas was considerably thinner. Here the breeze was beginning to freshen, and this was serving to dissipate the noxious chemicals. But even though the gas was becoming thinner and thinner, the young engineers knew better than to remove their masks too quickly.

Having reached the top of the gully, Dave decided to set off in the direction of the cliff where he had left the others of his detail. In order to make certain of the direction he pulled out a pocket compass for consultation. Then, more out of habit than because he wanted to know the time, he looked for his watch.

The timepiece was gone! It had disappeared along with the strap that had held it.

Dave was startled, and not without good reason, for the wrist-watch was one that had been presented to him on leaving for the front and was both handsome and valuable.

Like a flash it suddenly came to the young engineer where the watch had been dropped. He remembered now that he had looked at it when about to turn away from the pile of German shells which he had found hidden near the old wood trail. After looking at the watch he now remembered that something had struck his foot, which at the time he had thought was a stick or a stone. Now he felt sure it must have been the missing timepiece.

It would not be much out of their way to return to the vicinity of the cliff by way of the spot where the pile of shells had been discovered, and so Dave and Phil set off in that direction carrying Roger between them. The wind was now coming up strongly; and soon they felt it would be safe to remove their gas masks, and accordingly did so.

“Gosh! but I’m glad to get this off,” were Phil’s first words, after he had cautiously tested the air with his nose to discover if he could still detect the odor of gas.

Even though the mouthpiece on his mask had been broken, Roger had had little difficulty in using the outfit, and had not suffered from the poisonous attack. But his left ankle pained him not a little, and when, supported by his chums, he attempted to stand on his foot he made a decidedly wry face.

“Ouch!” he exclaimed. “Feels worse than ten thousand needles jabbing through it.”

“Don’t worry,” answered Dave kindly. “We can carry you just as well as not, can’t we, Phil?”

“Of course we can!” was the quick reply. “It will take us a little longer to reach the others, but what of that?”

“Dave, I hope you get your watch back. I know you’d hate to lose it,” said Roger, as the others prepared to pick him up once more.

“Oh, I’m almost certain I know where I dropped it,” was the young sergeant’s reply.

The booming of the heavy artillery in the distance had ceased, but now came another crash off to the southward.

“That’s thunder!” exclaimed Phil. “Looks to me as if that storm might be coming back.”

“It certainly did let down while it was at it,” remarked Roger. “I didn’t have to crawl down to the brook to soak that bandage for my ankle. All I had to do was to draw it over the bushes and grass around me and it got soaked in a minute.”

The veering of the wind once again made the atmosphere pure around them, and for this, as they drank in the fresh air, they were exceedingly thankful.

“I’ll tell you one thing—fresh air is like fresh water,” remarked Phil. “You don’t know how good both of them are until you can’t get them.”

“I can tell you I felt pretty bad down there in the gully all alone,” returned Roger. “Once or twice I tried to crawl out, but the pain in that ankle was so terrific it was too much for me. I was afraid that I might faint, and then if my mask got loose in any way it would have been all up with me.”

As they advanced Dave told of finding the pile of three-inch shells hidden in the brushwood. Roger was as much interested as Phil had been.

“Do you suppose they were put there lately, Dave?” questioned the corporal.

“I don’t believe so, Roger. I think they date back to some other time—probably some time before we were on or near this front. You know this part of France had been under fire for many months.”

The sky was growing dark again, and now came a flash of lightning at a distance, followed by a rumble of thunder. Then came more rain and several other lightning flashes, each one a little nearer than those before.

“We’re in for it, all right enough,” was Phil’s comment. “I wish we were back in the shelter of the cliff.”

“How far is that from here?” questioned Roger.

“At least a quarter of a mile,” answered Dave.

With the storm coming on again the wood grew rapidly darker, so that it was with difficulty that the young engineers picked their way through the tangle of brushwood and around the rocks and fallen trees. It was now raining steadily, and before long all were wet to the skin.

“It’s too bad I took you so far out of the way, Phil,” remarked Dave. “I suppose we might have gone on direct to the shelter of the cliff, and I could have come back to look for that watch some time later.”

“Oh, that’s all right, Dave,” was the quick reply. “We would have got wet anyhow. I want you to get your watch back first of all. It won’t do the timepiece any good to be lying out there in the wet.”

The three young engineers were still about a hundred yards away from the hidden shells when the storm seemed to burst directly over their heads with tremendous fury. There was a vivid flash of lightning, followed by a loud crack of thunder, and then off to their left they heard one of the big trees of the forest come down with a crash, carrying some small growth with it.

“Wow! that was some crack, believe me!” exclaimed Phil, after it was over.

“We can be mighty thankful we weren’t under that tree that was struck,” said Roger.

“It certainly is a heavy storm,” put in Dave; “and it seems to be growing worse every minute. Just look how dark it is becoming.”

“I hope it doesn’t get so dark you can’t see to find your watch,” said Phil.

The lightning and thunder had brought them to a temporary halt, but now they started to go forward again, the flash of lightning having left them in a darkness which was almost absolute.

“Be careful you don’t go down in some hole, Dave,” cried Phil, for the young sergeant was in advance, carrying Roger by the knees, while Phil in the rear supported their chum under his arms.

The words had scarcely been spoken when there came another jagged flash of lightning from the sky almost directly, so it seemed, in front of the young engineers. They saw the fork of electricity shoot down into the very midst of the spot where the German shells lay hidden. The flash of lightning was followed by a crack of thunder, and then almost immediately afterward came a tremendous explosion from the pile of shells as a number of them seemed to go off simultaneously.

There was an awful flash of fire, and then Dave and the others were hurled backward in a heap among the bushes and trees.