The girls stared wide-eyed at Betty while slowly the color drained from their faces. It was true they had been dreading just this news for a long, long time, yet now that it had come they felt strangely quiet and numb. They had much the same feeling as one who had received a stunning blow. Until the paralysis had passed there could be no pain. That would come later. "How do you know?" asked Mollie at last, in a voice that sounded strange even to herself. "Frank hasn't mentioned it." "He will probably, toward the end," Betty explained, while slowly her heart contracted and the tears welled to her eyes. "Allen didn't--not till the last sentence. It's only a line, but th-that's enough. He says not to be alarmed if his letters are delayed--it may be hard to get them through." "They are going to the front," Amy repeated dazedly, as if she found it hard to really believe. "When--did he say when, Betty?" "No, he didn't," said Betty slowly. "But you know Allen. He wouldn't have said anything about it if the time hadn't been pretty close at hand." "Why," cried Grace, catching her breath as though the thought had just occurred to her, "they may be in the front line trenches now! They may be--they may be--" And while the girls gazed at her in tragic silence, imagining terrible, unbelievable things, a moment will be taken to sketch briefly for the benefit of new readers the various exciting or amusing adventures which had befallen the Outdoor Girls in the days before the grim shadow of war had spread itself over the land. In the first volume of the series, entitled "The Outdoor Girls of Deepdale," the girls had formed a camping and tramping club and had tramped for miles over the country, meeting with many interesting adventures on the way. After this, one good time had followed hard on the heels of another, first at Rainbow Lake, then at a winter camp where they had novel and interesting experience on skates and ice-boats. At Ocean View some time later the Outdoor Girls had cleared up a mystery centering about a strange box they had found in the sand. Then had followed that splendid summer at Pine Island, when the girls had accidentally discovered a gypsy cave and had succeeded not only in rounding up the band of gypsies but in recovering several valuable articles that had been stolen from them. The four boys who were now facing the enemy in France had shared in their fun that summer, pitching camp near the bungalow of the girls. Their next adventure found the girls and boys again at Pine Island, but under greatly altered circumstances. America had just entered the great war, and the four boys had responded eagerly to the bugle call. Later they were sent to Camp Liberty for training, to which the girls soon followed them to work in the Hostess House.