In May 1944, 5 years since the declaration of World War II, three Royal Homing Pigeon Service war pigeons are flying across the English Channel with the White Cliffs of Dover in sight, carrying vital messages to Great Britain. Despite the poor weather conditions the pigeons have nearly reached their destination. They are, however, suddenly ambushed and attacked by a German enemy falcon called General Von Talon; two of the pigeons are instantly killed, yet the third, Mercury is taken as a prisoner of war.