"Well, if we can find the boys we'll just mildly hint that those chocolates are about due," observed Grace, and she and the others looked about for Will and his chums, little dreaming of the danger which, at that moment, menaced poor Amy. Those of you who have read the previous books of this series need no special introduction to my heroines. Others may care for just a brief one. The initial volume, entitled "The Outdoor Girls of Deepdale; Or, Camping and Tramping for Fun and Health," told how Betty, Mollie, Grace and Amy decided to go on a walking tour. Incidentally they solved the mystery of a five hundred dollar bill, and won the lasting gratitude of a Mr. Henry Blackford, a young business man. In the second book, "The Outdoor Girls at Rainbow Lake; Or, The Stirring Cruise of the Motor Boat _Gem_," there was a queer ghostly mystery on an island, but the girls were a match for it. As may be guessed from the title, the story has to do with boating, Betty having become the proud possessor of a fine craft. When Mollie Billette got her touring car the girls saw no end of good times ahead of them, and their hopes were fully realized. The third volume, named "The Outdoor Girls in a Motor Car; Or, The Haunted Mansion of Shadow Valley," involved the girls from the very start in a series of queer happenings. They could not discover, until the very end, why a certain girl fell out of a tree. And as for the strange manifestations in the mysterious old mansion--but there, it would not be fair to betray the secret in such a fashion. The beautiful Fall weather gave the girls a chance to make long tours in the car, and they enjoyed every minute spent in the open. And now they were on the edge of winter. A cold snap had frozen over the Argono River, on the pleasant banks of which was located Deepdale, the thriving town where our friends lived. And they were out enjoying the sport when Amy overheard the cruel words that sent her off crying. I might add something about the personal lives of the four chums, by saying that Betty was an only child, that Grace had a lovable brother Will, and Mollie a small brother and sister--Paul and Dodo--twins, who were alternately called the "cutest" and the "most mischievous" youngsters in existence. Of Amy's mystery I have already hinted. When Will Ford saw the danger in which his sister's chum was unconsciously placing herself he fairly raced forward. There was need to act promptly, and Will did so. Skating in a diagonal direction he fairly collided with the girl, and forced her out of her course, and away from the dangerous hole that yawned there just before her. "Amy!" Will cried. "What is the matter?" Amy looked up with a start, and Will saw that she had been crying. "I--I don't know," she stammered. "I guess I wasn't looking where I was going." "I should say not!" cried Will. "Look there!" and he pointed to the open water that seemed so black and ugly in contrast with the pure ice.