The strange and puzzling riddle of the ghostly avengers is moving to a rapid conclusion as Hop and Tank now in possession of almost all the facts go in to action to trap the man trying to ruin the Ace Flying Service. There are three suspects, Bert Craig, Vinney Stevens and Paul Conway, all partners in the airline

Inspector Fry reveals that the "ghost planes" are a front for someone trying to buy the airline. The ghost plane appears and Hop heads right towards it!