'This is the queerest sort of kidnapping case I've ever run into,' vowed Eddie Ross, U.S. member of Interpol, who himself had brought this full-sized headache across the Atlantic for Biggles to solve. In their quest for kidnapper Cornelli and his hostage Carlo Salvatore, Biggles & Co. are forced to maintain an aerial shuttle service between London and Scotland, but it was by the turbulent waters of a Highland salmon river that the last grim gun battle took place.