In a temple filled with ancient statues, the Hood plots to learn the secrets of International Rescue. He faces a statue of his brother Kyrano, who, because of "misguided" reasons, serves International Rescue. The Hood begins using his mental powers to try to influence Kyrano. On Tracy Island, Kyrano is thanking Jeff Tracy for all he's done for Kyrano and Tin Tin. Suddenly, Kyrano, collapses and screams in pain. The Hood concentrates harder, demanding to know when International Rescue will start operating. The writhing Kyrano finally gasps that the organization is ready now.
In a London airport lounge, Tin Tin waits to board her flight to Tokyo. A flight attendant comes by to notify her the Air Terrainean flight is ready, the maiden voyage of the Fireflash, an atomic-powered aircraft capable of Mach 6. On the tarmac, a saboteur dressed as a maintenance worker is planting an "auto-bomb explosive unit" in the Fireflash. The airliner takes off and quickly reaches cruising altitude and speed, Mach 5.3 at 250,000 feet. In a phone booth on the ground, the saboteur makes a sound-only call to the control tower, warning them of the bomb in the landing gear. It's set to explode when the aircraft lands, destroying it and releasing radioactive debris. When the call ends, the man removes a latex face mask to reveal the features of the Hood. The Fireflash captain is ready to go greet the passengers when the control tower notifies them of the bomb threat and orders them back to London as a precautionary measure.
On Thunderbird 5, John is monitoring worldwide communications when he intercepts a call from the tower to the Fireflash. As the Fireflash passes, the tower takes an automatic x-ray of the landing gear. The photograph confirms the bomb. The tower controller orders an evacuation of the surrounding area. The pilot says they can stay aloft for months, but the radiation shielding will deteriorate in just over two hours, bathing the passengers in radiation. On hearing that, John notifies Jeff on Tracy Island. Jeff dispatches Scott in Thunderbird 1 to survey the situation. Scott receives an update from John, then asks for heavy assistance. Jeff sends Virgil in Thunderbird 2.
In the control tower, Lt. Meddings suggests diverting a TX-204 target training aircraft to the airport, where he will dangle from a harness unreeled from the target drone bay and try to board the Fireflash. John receives the transmission and notifies Jeff and Scott, who hope it works. Meddings is strapped behind a drogue cone at the rear of the TX 204 and winched backward to the Fireflash behind. Alongside the aircraft, Meddings has the Fireflash pilot open a motorized inspection hatch. He makes it into the hatch and climbs hand over hand across a pipe to the bomb. But he can't reach it so he tries to go around the long way. Meddings grabs a wiring bundle, which pulls free, dropping him from the Fireflash. He's saved when his parachute opens at the last minute, but the Fireflash as only 30 minutes left. The tower personnel are resigned to hoping the bomb is a dud when they spot Thunderbird 1 on radar approaching at 7500mph. They've never heard of International Rescue, but are curious at the advanced aircraft. Scott demands that guards be posted around Thunderbird 1 to keep anyone from taking photographs. However, disguised as one of the airport police is the Hood, taking pictures with a camera in his cap badge. He also enters enters the cockpit and begins taking pictures. But the photo-alert goes off. At Scott's urging, the airport commander has police chase the picture-taker. The police lose track of the Hood. Scott calls for help from Lady Penelope.
Thunderbird 2 arrives, disgorging a master elevator car and two radio controlled elevator cars to set up on runway 29. Airport crash crews are put on alert at the end of the runway. Virgil drives from the master car, planning use the cars to create makeshift landing gear. He notices a fault with car 3, but it clears as the plane approaches. The cars speed up to match speed with the airliner. Just before landing, car 3 has its fault reoccur, veering off to crash into a parked airliner. Virgil repositions with elevator car 4 replacing the burning number 3 as the Fireflash goes around for another pass. On the second try, the cars get into position under the wings with a little difficulty. The airliner reverses thrust but can't stop in time. Virgil applies full brakes to all the cars. His master car slides out from under the nose, crashing on the side of the runway. The tires on car 4 blow and Fireflash skids to a stop with its nose on the ground. The tower commander is grateful. Scott reiterates they need utter secrecy and demands all aircraft be cleared for 100 miles around.
On a highway, Lady Penelope and Parker are in a high-speed chase in FAB 1. When the coast is clear, Parker uses a grille-mounted cannon to shoot the Hood's car. He crashes off the side, the ruined film spilling from his cap. Incensed, he vows revenge on International Rescue.
Back at Tracy Island, the family relaxes after their first successful mission. A doctor has been examining Kyrano after his "dizzy spell" but finds nothing wrong with him. He notices the newspaper story about the mysterious organization behind the recent rescue and wishes he could thank the people involved by shaking their hands. Jeff thanks the doctor for coming on the housecall and shakes his hand, with the doctor none the wiser that his wish has been granted.