Unravel a thrilling saga of camaraderie and intrigue in book four of The Hardy Boys mystery series, published in 1928. Follow Frank and Joe Hardy as they grapple with the unexplained disappearance of their closest friends, Chet and Biff, during a motorboat trip. The stakes are high, as Baldy Turk's gang think they've kidnapped Frank and Joe and, in a letter received by the Hardy Boys' Aunt Gertrude, are demanding ransom for their return. An investigation...