A geological survey team gets trapped when a huge Earthbreaking vehicle causes them to fall into a narrow crevice. Scott, Virgil and Kayo take off in Thunderbird 1, Thunderbird 2, and Thunderbird Shadow after the Earthbreaker takes out the responding GDF fliers. The vehicle's controller, known only as The Mechanic, attacks and damages Thunderbird 2, leaving Virgil no choice but to make an emergency crash landing back on Tracy Island. Meanwhile, Lady Penelope and Parker visit the Hood in Parkmoor Scrubs prison to find out more about this mysterious new villain. In the end, Scott evacuates the survey team while Kayo takes on the Mechanic. They barely make it out when the villain sets his vehicle to self-destruct.

Thunderbird 3 is called out to Europa, a moon of Jupiter, when a pair of documentarians fall into an ice ocean, leading Alan to make first contact with an alien lifeform.