On a sunny September afternoon two shelter tents stood in a mountain valley, on the south bank of a creek which, miles and miles below, becomes the Sweetwater river.Above the flap of each tent lifted a yellow pennant, in the center of which a blue beaver stood in an alert and listening attitude, his flat tail outstretched.A campfire blazed in front of the two tents, and some distance away four bronchos fed noisily on the sweet grass of the valley. Tinned provisions and cooking utensils were scattered here and there in front of the blaze, and four boys wearing the khaki uniform of the Boy Scouts of America were busily engaged in preparing supper.Those who have read the previous volumes of this series will require no introduction to Will Smith, George Benton, Charley (Sandy) Green, or Tommy Gregory. As will be remembered, they were all members of the Beaver Patrol, Chicago. Will Smith had recently been advanced to the important position of Scoutmaster, and George Benton had been elected to the position left vacant by the advancement of his chum, that of Patrol Leader. Besides carrying the badges of their offices and their patrol, the boys all wore medals showing that they had qualified in the Stalker, Ambulance, Seaman and Pioneer grades.