"Of course!" he said, to himself. "If there were people here they took them along with them. They wouldn't be likely to leave any French people, whose first idea would be to tell what they had seen! It's certainly lucky that they didn't see us. We'd be with them now, I guess."

It was spooky work exploring the abandoned inn in the damp, dark night and with the knowledge that German soldiers were probably no great distance away. It was less than a quarter of a mile to the edge of the wood that had assumed such an important aspect, and he expected at any moment to hear the footsteps of intruders. None the less he went about his task quietly and coolly.

"If they had any essence, they'd hide it," he said to himself. "They'd know that both armies would need it for automobiles and aeroplanes, and they'd try to keep any they had left. So it won't be in any of the usual places."

For that reason he did not even leave the main building to make a search in the stable that was used as a garage. Instead, he went into the cellar. Here it was still plainer that the Germans had passed through. His feet stepped into puddles of sticky dampness, and, using his flashlight, he saw that it was wine. The heads of casks had been knocked in; broken bottles, too, strewed the floor.

This, however, had not been wanton destruction, he was sure. It had an object, and that object had been to prevent the soldiers from getting anything to drink. Troops on an errand requiring such extraordinary secrecy as had been maintained in this case could not be allowed to drink any liquor. That would have spoiled in all likelihood the remarkable discipline of which Captain Greene had spoken.

But, once more, it was not his business to think of what he saw, or to speculate about it, but to find the petrol if any was to be found. And he stumbled upon the hidden store quite suddenly, and quite literally, too. In one corner of the cellar was what looked like a pile of kindling wood. Harry kicked it indifferently in passing, and was almost thrown when his feet encountered a resistance more solid than he had any reason to expect. He looked down, and there, under the kindling, were two ten-gallon cans of petrol!

"I knew it must be there!" he cried to himself. He was down on his knees in a moment, shaking the cans to make sure that they were full. One had never been broached; the other was nearly half full. And this second can was the one he took. That would be more than enough to get the monoplane back to headquarters, and there was no reason for burdening himself with too great a load. He picked up the can, and at the same moment his heart leaped up into his throat, for overhead there came the sound of heavy footsteps. For a moment he stood as if paralyzed, listening.

The footsteps continued; guttural voices sounded,—the voices of Germans. It was impossible to distinguish what they were saying; and it made no difference, in any case. The only point that mattered was that they were there; that they blocked the only means Frank had of getting away with the precious petrol he had so luckily found.

He was safe enough personally. Even if they were led to come down into the cellar the chances were all in favor of his being able to conceal himself. What he feared was that some use was to be made of the place, and that the men whose voices he heard would stay there, thus preventing him from getting out of the building and so getting the petrol to Greene. It was more than possible, he thought, that the German commander, knowing that the presence of his troops in the woods had been discovered, would decide to use this place for headquarters.

And what he could hear confirmed this idea. There was a continual tramping overhead. Men came and went. That seemed to indicate that the occupation was to be permanent. He racked his brains for some means of escape. Windows there were none in the cellar. He found no trace of a trap door, such as there would have been in almost any American cellar. And then the saving thought came to him like a flash. He debated for a moment, then decided that the risk was worth taking. First he took his can of gasoline to the steps. Then he poured a little into a broken bottle, and poured this, in turn, on the wood under which he had found the cans. He dragged the full can of petrol to the other side of the cellar. And then, very deliberately, he set a match to the gasoline soaked wood and retreated to the steps.