The Blue Envelope by Roy J. Snell, Fiction, Action & Adventure 7+

📗 Marian and Lucille seem to be in for the time of their lives -- in the worst sense.First they find a boy who seems exhausted from swimming, who must have been lost overboard from another boat. Taking him to their camp, they feed him broth and potatoes, and watch him fall asleep in exhaustion by the fire.Later in the night they hear a sound -- almost like oarlocks . . . and discover the boy is gone -- and along with him is their rowboat! But the boy was not acting alone, for they find footprints of two others . . . just as they hear their motorboat starting up, in the bay. So that, too, is being stolen -- and there they are, the two girls, trapped on this island off Alaska!