The Gray and Houseman mining operation now includes planet Mercury; it uses a moving vehicle that stays on the 'dark side' of the planet. However, when a malfunctioning pod leaves the vehicle stranded - and with the sun's blazing 'terminus' drifting ever closer -International Rescue are summoned to solve the problem.

When a rockslide pins Captain Taylor and a scientist in a Martian cavern, Virgil and Alan fly to the planet Mars and assist with the aid of Thunderbird 3 and a specialised Exo-Pod. However, circumstances in the cave lead Virgil to eject the air in his suit, leaving our heroes short on air inside a leaking cave.