At an Australian atomic station, a worker is giving a tour to some members of the press. He says that although this station is still on the secret list, he can tell them that the sea water so needed for this irrigation project is pumped to the station by the plant they can see on their left.

He says that naturally, the reclaiming of the dead lands of Australia takes up millions and millions of gallons of the sea water. He asks if there are any questions. One guy wants a statement on the safety factor, as there's always a certain amount of public concern over these atomic devices. The worker says this project is no more dangerous than the many atomic power plants setup all over the world. They appreciate that an accident could occur, but the chances are very, very slim. The press aren't too convinced, but he says that the reactor is under the complete control of the project staff -nothing can go wrong.

Nearby, the Hood is hiding. He takes a look around, and sees the reactor building. Inside is reactor controller Wade, who finds out from his assistant that the sightseers are still here. He says the public has got a right to be worried, as if there was an accident here the radioactivity would spread right across Australia. The assistant thinks there's no chance of that.

The Hood comes across the sea water plant, and starts taking photographs of it. But then a security guard sees him, and asks him what he's doing. As he starts blowing on a whilste and making a lot of noise, the Hood pulls out a gun and starts shooting at him. An alarm then goes off.

As the Hood hides behind a pipe, the security guard tells him to come out of there, and keep his hands up. The Hood shots at him again, and as he dives out of the way, the bullet hits a gas line behind him. This explodes, which quickly spreads fire across the entire building.

The building then explodes, spreading fire and debris to other buildings in the plant. The fire services are deployed, and an announcement is made over the PA system advising any unauthorized personnel to leave the base immediately. The press truck heads off.

Eddie Kerr says he just wants to get to a phone. As the explosions continue to occur all over the plant, the control staff are contact by the fire chief. He says that the fires are getting out of hand, and it looks bad. Control tells him to keep the fire away from the main plant. Wade thinks that if the fire gets to the reactor, this whole place could go up.

The reactor building is already surrounded by smoke. The Hood has moved away from the station, and says they haven't heart the last of him -he'll make the plans of those atomic stations his, if it's the last thing he does! Meanwhile, the press have gotten to some phones. They start reporting on the fire, and one guy says that there's a rumor that the fire has reached the reactors.

Inside the control room, Wade is trying to shut down the reactor. But he says it's no good, unless they can cut off the sea water intake, they can't stop it. The assistant says the reactor is racing away. They then get an update from control, who tell them that they've received orders to evacuate. Rescue aircraft are standing by, and Wade realizes that they're going to let this place destroy itself.

The rescue plane flies over the plant, and lands. The fire is now at the reactor building, and sets it ablaze. All of the remaining staff board the rescue plane, which turns around on the runway and then takes off.

Wade looks down on the plant, and says it'll be going up any second. He wishes there was a way they could have cut the intake. Inside the control room, the reactor control panel's light is now flashing on danger. Outside, the fire continues to get worse, until...

...the reactor explodes, causing an atomic mushroom cloud. Radioactive material is sent over the barren lands. As this is happening, another press conference is about to take place.

The press officer says they appreciate the cooperation of the press and television networks, and thanks them for responding so promptly. He then turns things over to General Speyer. Speyer tells everyone to relax, and gets straight to the point: it concerns the explosion at the atomic irrigation project last Monday. Eddie says he thought that was all over, they'd been asked to play it down.

Speyer says that was only because they've been trying to avert a panic. The truth of the matter is the explosion caused a radioactive cloud. They've been trying to disperse it, but have so far been unsuccessful. The cloud is continuing to move towards their major cities, so the public have got to be told. Unless the weather takes a hand and a strong wind springs up, for safety concerns Melbourne will have to be evacuated. The cloud continues to move across the wastelands, but then something happens -a wind does pick up, and blows it away.

The press are soon reporting that Melbourne has been saved, thanks to the atomic cloud moving away. One of the reporters says the wind came just in time, and supposes they can all breathe again. 12 months later, the press report on a new atomic plant opening.

The Hood is aware of the new station, and says a year ago he failed to in his attempt to steal the secrets of the new atomic stations. But now, a chance, a master plan that cannot fail! And with the fortune these secrets shall bring, his empire will grow, and he shall be invincible! Meanwhile, Thunderbird 3 docks with Thunderbird 5. John is going to be starting his month in the space station. Alan says it's good to see him, but asks why he's late. John says there was a lot on, what with Penelope arriving. Alan asks how she is, and John says she's very anxious to go on a rescue. Alan thinks if John's spell of duty is anything like his, Penelope is going to be unlucky. He's never known things to be so quiet.

At Tracy Island, Penelope says how thrilled she is to be here. It's the first opportunity she's had since International Rescue's operations started. Virgil says that from the reports they've been getting, it seems she's been having more adventures than they have! Tin-Tin thinks Penelope has had her share of excitement, but Penelope says she shan't consider herself part of the team until she's been out on a rescue. Jeff wonders where those cold drinks have got to.

In the kitchen, Parker and Kyrano are arguing about who gets to take the drinks out. Kyrano thinks it's his duty to serve the drinks, but Parker thinks he might want to see how it's really done. Kyrano says he's had no complaints from Mr Tracy so far. Parker thinks Jeff is quite sure he appreciates Kyrano is doing the best to his ability. Kyrano says he always has the honor to serve in this household, but Parker tells him he doesn't always have a butler from one of England's stately homes. As they continue arguing and pulling the tray back and forth, they eventually cause the glasses to fall and smash on the floor. Jeff thinks that, from the sound of it, they're going to stay thirsty.

At a government research unit, Professor Holden is giving a demonstration of their latest scientific project: the Mighty Atom. Although electronic, it behaves and looks like an ordinary mouse. The other people in the room are skeptical about it, and one says the taxpayers won't like paying four million bucks for that. Holden says they haven't called it the Mighty Atom for nothing, and says to watch closely.

Their furry friend contains a powerful miniature camera. It can be placed to photograph any foreign, alien or enemy installation that they wish. Professor Langley asks how he's sure the Mighty Atom will take the photographs you want. Holden says that the relevant information of any project can be seen on the dials of its control panels. Sooner or later scientists and technicians will look at those dials. The camera in the Mighty Atom has been electronically programmed to photograph the profile of the human face. He tells everyone they'll see how it works when he inspects the dials of a panel, and asks Langley to operate the remote control unit. Langley picks up the unit and uses it.

The Mighty Atom starts following Holden, and takes pictures of him at the control panels of a few computers. He then picks the Mighty Atom up and tells everyone he'll show them what he's got on the film. He plugs the Mighty Atom into a device, and then has the room's lights dimmed.

On a screen, images that the Mighty Atom took are displayed. Everyone starts congratulating Holden, with one guy saying this is a big step forward in espionage. Holden asks if there are any questions, so Langley asks what happens if the mouse is seen or approached? Holden says there is a safety factor incorporated in the design. If a human face moves towards it, then the Mighty Atom runs for the nearest cover and hides, like any real mouse.

Langley says he's very satisfied with that, but then his eyes suddenly start glowing. Holden passes out, whilst Langley looks around the room to deal with everybody else.

Langley is actually the Hood, who removes his disguise. With everyone else unconscious, he takes the Mighty Atom and goes back to his temple with it. There, he says that he at last has the means to spite his enemies. He calls the Mighty Atom a key that will open every door, and his power will grow as his knowledge increases. With the help of his new friend, the secrets of the world will be his!

The Hood arrives at the new atomic station. He uses a pair of binoculars to take a look around it, and says that now, he and the Mighty Atom will get what they came for. He heads into the station, and places the Mighty Atom down. He then uses the control unit to send the Mighty Atom on his way.

The Mighty Atom enters the reactor's control room. Inside is Collins, who is busy checking over various machines inside the room. The Mighty Atom starts taking pictures of everything, but as Collins sits down, he notices it staring at him. So the Mighty Atom flees, just as he gets up.

The Mighty Atom hides behind a computer. Collins says he doesn't know what this place is coming to, and goes to get Wade, the other reactor controller at the station. Wade doesn't believe him, and tells him to cut it out. The Hood decides to see what they've managed to collect, and recalls the Mighty Atom back to him.

The Mighty Atom leaves the control room, and goes back to where the Hood is. The Hood picks him up, and says this was a very good day's work. He then sees the gas equipment nearby, and it reminds him of what happened a year ago at the other station. He thinks that, whilst he's here, why not destroy the atomic station and bring out International Rescue? Then their secrets will be his for the taking!

At Tracy Island, Alan goes up to Penelope and says it's an emergency! Penelope asks if he means a rescue, and Alan says that's just what it is. She wants to be let in on it, and Alan says it's Scott -they don't know if they can save him! Penelope starts trying to take action, suggesting they alert Thunderbird 1 and Thunderbird 2, and where is Jeff? She then asks Parker to get the Rolls, but then asks Alan what the procedure is -she doesn't know it. Virgil and Gordon then appear and start laughing, as Penelope realizes this was all a prank. Gordon says they just couldn't resist it, and Virgil says they're as bored as she is. Penelope says at least Scott isn't in any trouble, but Gordon says that's where she's wrong. Virgil explains that Grandma caught him sampling a special cake she'd baked for tonight. Alan thinks Scott really does need rescuing.

At the station, the Hood has returned to his truck. He thinks that this atomic station is the ideal place for some International Rescue heroics, all they need is an accident. He says this should be easy to provide, and looks at some explosives he has in the truck. Inside the station's control room, Collins says there's a slight drop of pressure on the number ten generator. Wade says it showed up on the control panel, and he's adjusted it from there.

The Hood returns to the plant, and starts laying down several explosive charges. Meanwhile Wade says all of the routine checks are all completed. Wade says looks outside and says how fantastic it is -not so long ago this whole area was a desert, now some greenery has returned. Wade says that's the idea of the scheme: process the sea and oceans with atomic energy into fresh water, then pump it out into the Earth's deserts. The entire station is manned by just the two of them, as everything is fully automated. Outside, the Hood has moved away from the plant, and starts a countdown.

The explosives he set start going off, causing widespread damage across the station. Wade and Collins wonder what's going on, and switch the station to emergency control mode. But they can't control it, and see that control board five is going crazy. Wade thinks that this is sabotage, nothing else can explain it. Collins says the reactor is starting to race. Wade says he saw this happen before in Australia. Collins wants to get out of here, but Wade says he's seen what can happen. In two hours time they'll be an explosion, then a radioactive cloud will drift across Africa. They can't count on a wind saving them this time. Collins asks what they can do. Wade says the last time this happened, International Rescue weren't in operation. But that's who they're going to have to call now.

The Hood watches the explosions, and says they're waiting for the Thunderbirds. John picks up an emergency call from the station. He then reports this to Tracy Island, and explains that if the reactor explodes, then the radioactivity will do unthinkable damage. Jeff tells him to radio the station and let them know that help is on its way.

Jeff asks Brains what they'll need. Brains says the big problem will be the sea water intake. It'll have to be cut off underwater, so Jeff says this sounds like a job for Thunderbird 4. He tells Brains to alert Virgil and Gordon, and then tells Scott the destination is North Africa: a runaway reactor in the Saharan atomic station. It's possibly sabotage, but John will fill him in with the details once he's airborne. Penelope says Jeff must know how badly she wants to go out on a rescue. Jeff says this one is too dangerous, but when Penelope says she may not get another chance, he tells her to go with Virgil. Scott says here he goes, and heads off to Thunderbird 1.

Virgil heads off to Thunderbird 2 the usual way, whilst Gordon and Penelope take the passenger chute. Virgil selects pod 4, and with everybody onboard, he gets Thunderbird 2 ready for launch.

Thunderbird 1 also takes off. Back at the plant, Collins says the chain reaction seems to be speeding up. Wade says he's put the information through the computer, and it says they've got just one hour left before the whole place goes sky high. In Thunderbird 2, Penelope says this is an absolutely fantastic experience. Gordon is glad she's enjoying it. Penelope says these machines are quite fabulous, and Virgil says sure they are -that's why there are people who'd stop at nothing to learn their secrets.

Collins says whoever did this is probably still around. But they then see Thunderbird 1 coming in to land. As it does, the Hood is waiting in some bushes nearby.

Thunderbird 2 comes to a stop above the sea, and drops its pod into the water. The pod door opens and Thunderbird 4 heads down the ramp, then enters the sea. Gordon moves Thunderbird 4 into position, which is at the sea intake. He radios Scott and tells him he's in position, and is awaiting further instructions.

Scott tells him ok, and says that he and Virgil will try to get the reactor under control. Once done, he tells Gordon he'll have to stop that water coming through the intake at the exact second, otherwise they'll all go up. Wade says the reactor is running away, and International Rescue have got just 20 minutes. Outside, Thunderbird 2 lands near the station.

The Hood watches it, and says they've at last all arrived. He tells the Mighty Atom to go and get him those photographs, and sends it off to Thunderbird 2. Virgil tells Penelope he's going to join Scott, so she should stay here and keep radio contact open. Penelope says she will, but if they want her to help them inside, they don't need to hesitate to ask. At Tracy Island, Brains suggests they call the station, but Jeff says John is now coming through to them.

John reports on what's happening: Gordon is standing by, awaiting instruction to destroy the sea intake. Scott and Virgil have donned protective clothing, and are going into the reactor control room. Brains says that means they're going to try and bring it under control with the rods. At the station, explosions are taking place near the reactor building. Inside, Scott and Virgil start using the rods.

They are told that they've got 5 minutes left. Virgil pushes one of the rods in, and gets control board 3 back under control. Wade says there are two minutes left.

Virgil and Scott continue to carefully use the rods, and get control board 4 back under control. They are told they have 90 seconds left, so they then get control board 5 fixed. With that done, Scott contacts Gordon and tells him to fire missiles. Gordon fires off two missiles.

These hit the water intake, destroying it. Collins says that International Rescue have done it! Meanwhile, the Mighty Atom arrives inside Thunderbird 2.

It also finds Penelope, who starts screaming. Later on, Thunderbird 1 takes off, and heads back to Tracy Island. Moments later, Thunderbird 2 also takes off.

Virgil is laughing, but Penelope fails to see why. She just doesn't like mice, that's all. Virgil says he'll change the subject, and contacts Tracy Island. He says they're going to pick up Thunderbird 4, and will then be returning to base. Meanwhile, the Hood has returned back to his temple, and says he at last has the information he requires.

He plugs the Mighty Atom into a device, which displays the photographs on a view screen. However, he is outraged when he sees that the only photographs it has taken are all of Penelope cowering -it hasn't taken any photographs of Thunderbird 2 at all! He calls the Mighty Atom a stupid, foolish, idiotic failure, and starts hitting it until it is destroyed.