The spies have a vital mission - they must protect a ship carrying the last component required to make a nuclear bomb. Other ships carrying nuclear parts have been raided by pirates and MI9 have intelligence to suggest that this ship will be targeted. The team use Frank's mini-submarine to follow the ship, in an undercover, underwater mission. Meanwhile, Frank is very worried about the team since his cousin Charlton went missing in the same waters some years back and was never found. The spies are making good progress underwater when the ship is attacked and the remaining nuclear component is stolen. Suddenly a giant tentacle wraps itself around the spies' mini-sub and starts to drag it down. The spies are captured by the nuclear-stealing culprit, a man known as the Octopus! He locks them in an airtight container in his lair, turns off the oxygen and makes off with the nuclear part. His mission is to fire the nuclear sub into a polar ice cap and submerge the entire planet in water. Will the spies stop him before it is too late?