While returning from a mission, Thunderbird 2 is seriously damaged when it comes under attack from a new, high-speed U.S. Navy strike vessel, the U.S.N. Sentinel. After an operation to move the Empire State Building disastrously ends in the tower's complete collapse, Jeff asks that Thunderbird 4 be transported onboard the same ship to the mouth of an underground river to reach a reporter and his cameraman who are trapped beneath the wreckage.

Brains and Tin-Tin set off on an expedition to retrieve sunken treasure from Lake Anasta. The Hood has also set his sights on the riches and plans to put both Brains and Tin-Tin in grave peril.

International Rescue's security is jeopardised when Tin-Tin's close friend Eddie Houseman, who recently visited Tracy Island, takes drastic action to save his road-construction company's threatened contract by planting explosives to tear open a jungle mountainside, and the ensuing chaos leaves him trapped on a cliffside in a truck with another case of explosives on board.

The Sun Probe rocket and its crew are locked in a collision course with the Sun, prompting the launching of Thunderbird 3 – but International Rescue itself requires saving when Thunderbird 3 is unable to escape the Sun's gravitational pull.

The Hood plans to corner the Thunderbirds vehicles by drawing them out to an emergency at an atomic irrigation plant in the Sahara, then photographing them with a miniature camera disguised as a mouse.

A criminal organisation steals classified plans. Working in conjunction with a British Secret Service agent, Lady Penelope must recover the material to save the world from total destruction.

An unscrupulous investor attempts to recruit Lady Penelope into funding his automated, cross-country monorail building project. Jeff volunteers to ride the prototype, but he, Brains, and Tin-Tin find themselves trapped onboard, and with no possibility of escape, when it is discovered that the monorail train is speeding towards a stricken bridge.

When a new growth hormone is accidentally released into a South American river, a house is besieged by alligators – now many times their normal size. International Rescue must subdue the reptiles and save the house's occupants.