One year later, the disguised Hood hypnotises delegates at a science conference and steals the "Mighty Atom" – an artificially-intelligent roaming surveillance device that looks like a mouse.
He then decides to exploit the situation further by creating a disaster to which the newly-formed International Rescue will respond, giving him an opportunity to use the device to steal the secrets of the Thunderbird machines.
One of 11 Thunderbirds scripts that were originally filmed as 25 minutes and later extended, "The Mighty Atom" was initially set almost entirely in the Sahara, with events in Australia being recalled briefly in flashback.
To lengthen the story, the series' writing team effectively split the episode in two by prefacing the main action with two new acts showing the Australian nuclear disaster in detail, as well as the Hood's theft of the Mighty Atom.
Certain scenes were altered to create this format; these include one of a news conference in Melbourne, which was shortened, and another in which the Tracy brothers play a practical joke on Lady Penelope, which was removed completely.
[5] Tom Fox of Starburst magazine is more positive, arguing that the episode contains "plenty of curious aspects" to compensate for the Hood's "outlandish" plans; he gives a rating of three out of five.
[3] Marcus Hearn, author of Thunderbirds: The Vault, considers the "sinister" music accompanying these scenes to be the episode's most effective element; however, he believes that the appearance of Penelope and Parker "clutters" the plot.
[7] In her 1991 autobiography, Sylvia Anderson wrote that the Mighty Atom itself "strains credibility" while comparing the nuclear explosion in the episode's first act to the real-life Chernobyl disaster.