The quartette was completed by Mollie Billette, often called "Billy." Mollie was the daughter of a well-to-do widow of French ancestry, and the girl was a bit French herself in her general make-up. In our first volume, entitled "The Outdoor Girls of Deepdale," the particulars were given of the organization of a camping and tramp club by the girls, and of how they went on a tour, which brought them many adventures. After this first tour the Outdoor Girls went to Rainbow Lake, and then took another tour, this time in a motor car. After that, they had some glorious days on skates and iceboats while at a winter camp, and then journeyed to Florida, where they took a trip into the wilds of the interior, and participated in many unusual happenings. Returning from the land of orange groves, the girls next took a trip to Ocean View. Here they had a glorious time bathing, and otherwise enjoying themselves, and also solved the mystery surrounding a box that was found in the sand. During those strenuous days the girls had made many friends, including Allen Washburn, who was now a young lawyer of Deepdale. Allen had become a particular friend of Betty's, and this friendship seemed to be thoroughly reciprocal. Will Ford's particular high-school chum had been Frank Haley, and as a consequence, Frank had been drawn into the circle, along with Roy Anderson, another young man of the town. These young fellows often went off camping, and usually in the vicinity of where the girls had planned to spend their outing days. Deepdale was a picturesque city of about fifteen thousand people, located on the Argono river, which, some miles below, emptied into Rainbow Lake. Back of Deepdale was a rich farming country, which tended to make the town a prosperous one. Returning from Ocean View, the girls started on a new outing, as related in the volume before this, entitled "The Outdoor Girls on Pine Island." The girls occupied a bungalow, which had been turned over for their use by an aunt of Mollie Billette. The boys were in a camp near by. Quite by accident both girls and boys had stumbled upon a gypsy cave, cleverly hidden in the underbrush, and had afterward succeeded in rounding up the entire gypsy band, incidentally regaining some property which had been stolen from the girls. Now, at the time our story opens, the Outdoor Girls were again at Pine Island, in the cottage lent them by "Aunt Elvira"; but times had changed, and they were no longer solely upon pleasure bent. The grumbling, menacing unrest of war seemed in the very air they breathed, and from dawn to evening they thought of very little else. Now at the ringing shout, "I've volunteered," they were on their feet, fairly trembling with excitement and eagerness. "Allen, Allen!" cried Betty, the color flaming into her face. "Oh, I'm so glad! I'm so glad!"