In a secret bunker, the Hood watches a combat demonstration of a brand new jet fighter. Although he is deeply impressed, he is informed by his employer, General Bron, that it is second in performance to the British project, Red Arrow. The Hood is charged with destroying Red Arrow to ensure the superiority of Bron's fighter, with the promise of great riches in return. Soon, London International Airport is placed on maximum security alert while a test flight of the latest Red Arrow jet is undertaken. Although the tests begin well, the plane inexplicably deviates from its flight plan before entering a steep nose-dive and crashing with the pilot, Race, still aboard, while the Hood watches triumphantly. The project's supervisor, Colonel Tim Casey, is devastated by the loss and takes time off to visit his old friend, Jeff Tracy, at his home in the South Pacific.
Casey Visits Tracy IslandEdit
At Tracy Island, the family are enjoying a quiet day when the radar detects an unidentified aircraft approaching the island. It seems to dive for an attack on the villa, then unfurls a banner to greet the family as Casey arrives. Casey discusses the events with the Tracy family, and they all agree that the crash seems to have been caused by sabotage. Brains puts together a small device that can be placed aboard Red Arrow to inform the pilot if the plane is being diverted by an outside influence. Casey's pilot, Goddard, takes the equipment back with him to London airport ready for the next test flight.
Sure enough, the flight strays off course and Brains' diversion detector strongly registers an outside force. Unknown to the staff, the Hood has placed a device of his own at the base of a nearby telecommunications tower that attracts Red Arrow. A powerless Goddard has no choice but to eject to safety, leaving the jet to crash into the tower. The crash severely damages the structure, leaving two men, Jim and Stan, trapped in the control room at the top. Worse still, a heavy storm is just blowing in. The men call for International Rescue's help, but with Tim Casey on the island the team cannot launch their Thunderbirds without compromising their secrecy. Acting quickly, Tin-Tin persuades Casey to join her on a scuba dive to an underwater cave in hopes of seeing a rare tropical fish. Once they are out of the way, Scott takes off in Thunderbird 1 and Virgil and Alan in Thunderbird 2.
Booster Mortar in ActionEdit
They land a safe distance from the tower and Virgil brings the Booster Mortar out of the pod. Alan dictates the correct elevation angle and Virgil fires a metal case, containing low-altitude descent packs, through the tower's window. Jim and Stan put on the gear and leap clear of the control room just as the tower gives way. While the men float safely to the ground, Virgil notices an odd piece of equipment in the wreckage: the Hood's diversion device.
Convinced that Red Arrow is no more, the Hood speeds away from the crash site. To his annoyance, he is chased by a police car, causing him to charge recklessly through a roadblock. Before he can react, he sails off a broken bridge into the valley below; the police officers were simply trying to warn him that the bridge was out. His van crashes into the river and gradually fills with water, as General Bron rebukes him on the radio for failing to halt the Red Arrow project.
Good News For CaseyEdit
Scott, Virgil and Alan return to Tracy Island, where Casey is beginning to tire of his and Tin-Tin's vain search for rare fish. Once the Thunderbirds have returned to their hangars, she agrees to take Casey back to the villa. As they arrive, Jeff greets Casey with the good news that International Rescue discovered the cause of Red Arrow's crashes, so the project can continue. Casey wastes no time in packing up to return to London, and as he flies away he unfurls another banner from his plane, this one thanking Jeff Tracy.