The Hood infiltrates an atomic station in Australia, to take pictures of various machinery. He is seen by a security guard, and gets into a shootout with him. One of his shots hits a gas line, which causes an explosion. Things quickly escalate, resulting in more explosions that threaten the station's main reactor. The Hood and all of the staff there evacuate, and the station is destroyed when the reactor explodes. A radioactive cloud is also released, but it is blown away from Melbourne thanks to a strong wind. One year later, a second station is opened, this time in North Africa.

Penelope is visiting Tracy Island, and is desperate to go out on a rescue. Meanwhile the Hood, under the guise of Professor Langley, attends a demonstration by Professor Holden. Holden reveals the Mighty Atom: an advanced device that looks and acts like a mouse, but has a powerful camera inside it. The Hood steals the Mighty Atom, and intends to use it to take photographs at the new atomic station.

The Hood goes to the station and gets his photos, but then recalls the explosion at the Australia station. He decides he could use the Mighty Atom to take pictures of the Thunderbirds, and sets several explosive charges around the plant. The plant is mostly automated, with just two workers, Wade and Collins, operating it. After setting the charges, he retreats to his truck and sets them off, causing widespread damage across the station. With the reactor again in danger, Wade and Collins contact International Rescue. Thunderbirds 1 and 2 are sent out, with Thunderbird 2 carrying Thunderbird 4 in its pod. Penelope convinces Jeff to let her go along, so she rides with Virgil and Gordon in Thunderbird 2.

Thunderbird 2 drops its pod, and Thunderbird 4 enters the water. The plan is for Thunderbird 4 to fire missiles at the stations water intake once Scott and Virgil have got the reactor under control. As Gordon waits in Thunderbird 4, Scott and Virgil use rods to bring the reactor's boards back under control. Once this is done, Scott tells Gordon to fire missiles. Gordon has Thunderbird 4 fire two missiles, which destroy the water intake and save the reactor.

Meanwhile, the Hood has sent the Mighty Atom into Thunderbird 2, where it starts taking lots of pictures. Penelope, who was waiting in Thunderbird 2, sees it, and starts screaming. Later on, the Thunderbirds are heading back to Tracy Island. Penelope fails to see why Virgil is still laughing at her encounter with the mouse -she just doesn't like mice, that's all. The Hood returns with the Mighty Atom to his temple, where he plans to look at the photographs of Thunderbird 2.

However, he is outraged when he finds that the Mighty Atom has actually only taken photographs of a cowering Penelope -there are no photographs of Thunderbird 2 at all! He calls the Mighty Atom a stupid, foolish, idiotic failure, and starts hitting it until it is destroyed.

Notes

-The Australian plant scenes were not in the original, shorter version of this episode. They were added to make it longer.

-This is the only episode to feature all five Thunderbirds, and also the only episode to feature all of the regular cast.

-The aircraft used for evacuating staff of the Australian plant was previously used as a target carrying aircraft in Trapped in the Sky.

-One of the shots of the Hood driving his truck across a desert was actually taken from The Uninvited.

-The Hood seems to take a huge gamble with his plan -did he ever consider that International Rescue might not make it to the site in time, or fail to save the plant? Good job for him they succeeded.

Errors

-During this shot, an explosion is so powerful that it causes a moving car to get launched up into the air. It lands on its wheels and keeps going though.
-The two newspapers seen in this episode have the date of Friday December 24th 1964 -even though the series it meant to be either set in the early 2000s or 2064. Stranger still is the fact that December 24th of 1964 was actually a Thursday rather than a Friday.
-The Kyrano statue is shown twice in the episode, using footage from Trapped in the Sky. The Hood usually uses this to speak to Kyrano, and whilst Kyrano does appear in the episode, the Hood never tried to contact him -so why show the Kyrano statue?
-When the photographs of Holden are displayed, the Holden puppet can be seen moving slightly in each photo.
-Whilst the Mighty Atom is supposed to be able to only picture human faces, the Hood manages to take pictures of the African plant when nobody is in the room (maybe he reprogrammed it?).
-The Hood views this building with his binoculars. However this building never seems to be there for any other shot of the station.
-Scott's mobile control is the wrong equipment -if you look at it, it's actually got parts of the safety beam control from Thunderbird 3 on it, as seen in Sun Probe.
-Again, when the photographs of Penelope are displayed, her puppet can be seen moving slightly in each photo.