- "I fail to see why you're still laughing, Virgil. I just don't like mice, that's all."
— Lady Penelope Creighton-Ward
The Hood's first attempt to steal the secrets of a nuclear power plant ends in disaster. One year later, he uses a mechanical mouse called the "Mighty Atom" to successfully photograph an identical plant, then deliberately sabotages the installation to lure out International Rescue and obtain pictures of their equipment.
- Main article: The Mighty Atom/Storyline
- Main article: The Mighty Atom/Transcript
- Jeff Tracy - Peter Dyneley
- Scott Tracy - Shane Rimmer
- Lady Penelope Creighton-Ward - Sylvia Anderson
- Virgil Tracy - David Holliday
- Alan Tracy - Matt Zimmerman
- Brains - David Graham
- Parker - David Graham
- Tin-Tin Kyrano - Christine Finn
- Gordon Tracy - David Graham
- John Tracy - Ray Barrett
- Kyrano - David Graham
- Grandma Tracy - Christine Finn
- The Hood - Ray Barrett
- Eddie Kerr (2nd Reporter) - Matt Zimmerman
- Reactor Controller Wade - Ray Barrett
- Reactor Controller Collins - David Graham
- General Speyer - Ray Barrett
- Professor Holden - Peter Dyneley
- Reactor Control Assistant - Shane Rimmer
- Press Officer - Matt Zimmerman
- Australian Plant Tour Guide - David Graham
- 1st Reporter - Peter Dyneley
- 3rd Reporter - David Graham
- Australian Plant Fire Chief (voice only, not seen on screen)- Ray Barrett
- Australian Plant Guard - David Graham
- 1st Scientist - Ray Barrett
- 2nd Scientist - David Graham
- 3rd Scientist - David Holliday
- Australian Plant Tannoy - (voice only, not seen on screen) Sylvia Anderson
- Australian Plant Control (voice only, not seen on screen) - David Graham & Ray Barrett
- ?? - John Tate (?)
- Atomic Irrigation Station Tour Bus
- Press Conference Guard
- Research Unit Guard
- 4th Scientist at Professor Holden's Demonstration
- 5th Scientist at Professor Holden's Demonstration
- TV Reporter (Unnamed)
International Rescue Equipment UsedEdit
Non-International Rescue Equipment UsedEdit
- Atomic Irrigation Station (Australia)
- Eastern Australian Fire Department
- Government Research Unit
- The Hood's Temple
- Melbourne Herald Newspaper
- Press Conference (Australia)
- Saharan Atomic Station
- Sea Water Intake (Atomic Plant)
- Not counting the feature films, this is the only episode in which all Thunderbird craft appear.
- This is also the only episode in which all of the major characters appear.
- Originally a half-hour episode filmed in late 1964, it was extended in mid 1965.
- For subsequent 'cliffhanger' formats broadcast in some countries, the first installment ends with The Hood gloating in his temple that the secrets of the world will soon be his.
- The Target Carrying Aircraft first seen in Trapped in the Sky returns and is used by the Australian Atomic Station workers to escape from the nuclear explosion at the start of the episode.
- The Conference Hall's exterior set makes an appearance, and would go on to be reused in Cry Wolf, The Impostors, and Ricochet as entirely different buildings.
- The newspapers seen rolling off the presses after the radioactive cloud is blown away are actually copies of the Coventry Evening Telegraph.
- One of the very few times we see Thunderbird 2 flying without a pod.
- At the meeting with Professor Holden, The Hood is under the guise of one 'Professor Langley'.
- This is the only episode where the first line of text (the word "The") is in a smaller font size than the next line of text ("Mighty Atom").
- Main article: The Mighty Atom/Goofs
- French: Sabotage à l'usine atomique
- German: Die Supermaus
- Spanish: El poderoso átomo; El átomo poderoso (DVD)
- Italian: Nube sull'Australia
- Dutch: De geheime foto's (TV) De machtige atoom (VHS, DVD)
- Japanese: 原子炉の危機
- ↑ According to IMDb.com, John Tate voiced "various characters" in this episode.