Two Australian boys are playing their favourite game — "International Rescue" — when their "distress" call is picked up by John Tracy on Thunderbird 5. After a tour of Tracy Island, and a warning not to use their radio again, the brothers are returned home. The Hood then tricks the boys into an old mine shaft before stealing secret photographs from their government agent father. This time the brothers' SOS is real, but International Rescue refuses to believe them.
