At Cape Kennedy, it's 35 minutes until lift off for the Sun Probe. The solarnauts are taken inside the rocket, as Colonel Benson states that lift off will be in 24 minutes. The solarnauts -Camp, Harris and Asher -take their lift off positions. Harris reports their first module check is a-ok.

Benson reports that lift off will take place in 20 minutes. He puts out an alert and states for all launch areas to be cleared. Some vehicles move away from the launch pad, and then a thrust check is performed. Benson says it's a 17 million pound thrust, and increasing.

He says the thrust check is green. He then says that it's a 20 million pounds thrust and it's steady. He has the gantry move away from the Sun Probe, and contacts Harris. He tells him and the others that they're all rooting for them. Harris thanks everyone at solar control.

The fuel injectors are then retracted, and the entire unit moves underground. Benson conducts a 10 second countdown, and the Sun Probe then takes off with full power. Benson says that the Sun Probe looks good, as the rocket heads straight up into space. He says that project Sun Probe is on!

The entire thing is revealed to be a recording, which the Tracy family are watching. Jeff thinks that a rocket launching never fails to give him a kick. Eddie Kerr then reports that the film they've just watched was from a week ago, but within the hour they hope to bring them live pictures direct from Sun Probe itself via their latest tel-radio cameras. The object of the mission is to capture a few fragments of matter released by the sun

Eddie then turns things over to Professor Heinz Bodman. Jeff asks where Brains is, as he thinks he'd want to hear all this. Scott says this is old stuff to Brains, and he's in his workshop playing around with his latest invention. Brains is working on Braman, a robot he has constructed. Brains says he's going to test Braman's secretarial characteristics. Brains asks what his appointments for today are, and after a few seconds Braman lists them off.

Scott thinks the robot is improving nicely, but Brains still thinks Braman is late with his responses. Scott tells him when he's through there is a very interesting program about the Sun Probe on the air. Brains tells Braman he has such a lot to work on still. He wonders about teaching him chess, as it might improve his mathematical powers. Meanwhile, Bodman says that the solarnauts will release a radiation sealed refrigerated probe.

The probe will then fly through a prominence, and automatically collect particles and matter from the flare. This will give them a piece of the sun. Eddie says it's a dangerous mission, but all foreseeable protective measures guard the solarnauts against the sun's heat and radiation. 20 foot thick protective walls surround the solarnauts. Inside the Sun Probe, Asher says that their instruments are reducing the sun's glare 10 million times.

They look at the area they're going to shoot the probe at, and Harris says they'll be going into orbit in 38 minutes. Camp says that's the tricky bit, as if they miss the orbit, they could end up in the sun. The internal temperature starts to rise, so Harris orders for the refrigeration to be increased by two steps. Camp says it's a morbid thought, but without the auto refrigeration unit, they'd simply melt away. The Sun Probe continues on.

Jeff says the Sun Probe will be going into orbit soon, and thinks Brains won't want to miss this. But Brains is teaching Braman how to play chess, wanting to try and make him think quicker. Braman then makes a move on the chessboard, and Brains thinks it was a good one.

Jeff asks Brains if he wants to watch operation Sun Probe. Brains says he'd prefer to fix Braman, as he's still far too impulsive. Jeff says the Sun Probe will be going into orbit in 5 minutes, but Brains says it's 4 and one quarter minutes to be precise. Jeff thinks Brains knows the Sun Probe routine by heart.

Asher says the orbital firing will commence in 90 seconds. The retros are then fired, slowing the Sun Probe down. Harris looks at the monitor and says they're on the correct orbit. The radiation and temperature levels are checked, and Asher and Camp say they're a-ok. Asher then says it's 20 seconds until firing time for the probe.

The probe is then fired, which blasts off from the very front of the rocket. Eddie says the Sun Probe has been fired, and they'll give then all the details as they're received from the spaceship. Meanwhile, Braman makes another move on the chessboard. Brains thinks Braman is showing better powers of humanistic reasoning, so if he increases the defusory isobar rating, Braman should react a great deal faster. But he guesses he'll never succeed in creating a robot with a finer brain than a human.

Harris says the probe is going fine, straight for the prominence. They watch as the probe goes through the flare, and makes it. Camp says they need to get that probe, and Asher says then they can go back to Earth. Eddie says they've just heard that the probe has collected matter from the prominence, and is now on its way to rendezvous with the main ship. Their tel-radio then displays the Sun Probe, showing the probe reattaching to the rocket. Jeff says they've pulled it off, but Brains then appears, and says he doesn't think they're going to make it.

Jeff says everything is going fine. But then Eddie reports that something's wrong. In picking up the probe, the main ship has locked its course, and the tracking stations report the spaceship is heading on a collision course with the sun!

Brains thinks that when the probe was collected, the solar ship has to steer on a collision course with the sun. Alan thinks that was meant to be part of the plan, and Brains says it was. But he's figured that the radiation level at that distance from the sun could interfere with the ship's control system. Jeff says that must mean the solarnauts can't fire the retros and break away. Brains says that as a safeguard, the control center on Earth can send a radio beam to fire the ship's motors by remote control. Scott asks why they don't do that, and Brains thinks they must be trying it right now. But he has severe doubts that their beam will penetrate the radiation either.

Colonel Benson is then seen on the TV screen, making an important announcement. He says that all efforts to alter the spaceship's course by firing the retros by radio beam from Earth have failed. He now has a vital request to make: if International Rescue are watching, he asks for them to communicate at once, as this is vital -they need their help. Jeff asks Tin-Tin to get him through to Cape Kennedy. Jeff talks to Benson, and says they'll attempt a rescue. But this is a tough one. Benson says he can say that again, and offers him good luck.

Asher says to try the retros again, but Harris says it's no use. The circuit is dead, and Camp says it's the radiation, it's at an all time high. As the temperature increases, Harris has the refrigeration levels increased again. Camp guesses the radiation level is too high for the Earth to get the safety beam through, as they're too close to the sun. Harris says they're getting closer to the sun every second.

The Tracy family hold a meeting. Jeff says the Sun Probe rocket is heading straight into the sun, and unless they can fire the retros to make it turn round, those three solarnauts are doomed. Brains says the only solution is for them to fire the retros by radio beam. Scott says the radio complex on Thunderbird 3 is the obvious choice. Virgil thinks the transmission range of Thunderbird 3 isn't powerful enough, but Thunderbird 2's transmitter would stand a much better chance. Scott thinks that would apply if both crafts were at ground level, and Alan says they could take Thunderbird 3 into space to get through much more effectively.

Jeff wants to know what opinion Brains has on this. Brains says they might be underestimating the heat and radiation resistances of their own spacecraft. But the transmission potential of Thunderbird 2 could certainly be tremendous. Tin-Tin says they've got to make their minds up soon, as the whole world is waiting for International Rescue to act, and after 3 hours they're no nearer a decision. Gordon says both Thunderbird craft have an equal chance of success of failure. He suggests they gamble on one or other of them paying off. Jeff agrees, and says they'll launch a two-pronged rescue attempt. He wants Thunderbird 3 launched as soon as possible, and asks Brains when that can be. Brains says the radio equipment will have to be modified, but launching can take place soon after sun up.

Jeff tells him to go and organize that now. He tells Virgil to go to the computer room and work out what point is best for Thunderbird 2 to project a safety beam towards the Sun Probe, and to also get Grandma to organize some auxiliary clothing. Alan says they'll need someone extra to operate the safety beam, so Jeff says to take Tin-Tin along. Sometime later, everyone is ready to board Thunderbird 3. He tells them all good luck, and says to Tin-Tin that this is her first mission -make it a successful one. Tin-Tin says she'll do her best.

She, Alan and Scott then head straight down, as the sofa they're sat on withdraws into the floor. Moving on a track, the sofa moves towards Thunderbird 3's hangar, where it comes to a stop right beneath the spacecraft. It then moves upwards, taking the three inside it.

Alan tells everyone to take up launch position, as he goes to Thunderbird 3's control room. He tells the others to standby for blastoff, and soon Thunderbird 3 launches. It heads out through Tracy Island's round house, and Alan says the blastoff has been a-ok. Thunderbird 3 leaves Earth's atmosphere.

Scott heads up to the control room, and Alan tells Tin-Tin to get the electronics side lined up. They'll be in the danger zone in about 65 hours. Tin-Tin says she's already started on it. Thunderbird 3 continues to move away from the Earth, and heads towards the sun.

Back on Earth, Virgil and Brains are running through a checklist of things they need to take with them. Brains decides they need to take two snow dispersal units with them, as it's going to be pretty cold out there on the mountain. Virgil asks about the transmitter truck, and Brains says it's already in the pod. He says they should take the mobile computer too, just in case. He says it's right over there, and looks towards a box. Everything gets into Thunderbird 2, and Virgil and Brains take off in it.

As Jeff and Gordon watch them leave, Jeff admits he's never been so unsure of the success of a mission before. Unless Virgil or Alan gets in transmission radius of Sun Probe, the three men in that rocket are lost. In the Sun Probe, Harris says there's just 24 hours to go. Camp says to crash into the sun is like a nightmare, and Asher says it's a nightmare he's had many times. Harris says there's still time, but Asher wants to know why Earth doesn't do something. They then hear the radio, as Alan says this is International Rescue.

Alan explains they're going to try and fire their retros from space. Tin-Tin says they are 2 hours away from the calculated release area. Scott says the cabin temperature is increasing rapidly, and they can't go much closer. Alan says to try it now, so Tin-Tin operates the safety beam. Alan and Scott see that the beam is nowhere near close enough to the Sun Probe yet.

Scott says they're 4 hours short, and Alan thinks this means they'll have to go much closer to the sun than was estimated. Tin-Tin asks if they can stand the increased heat and radiation, and Alan says on paper no. But they can't just abandon those 3 guys. He contacts his father and explains what has happened. Jeff thinks the problem is Tin-Tin, can they ask her to risk her life further? Kyrano then appears and says he couldn't help but hear his words. Tin-Tin is his daughter, and he thinks he can say what her answer to the problem would be. Jeff says he knows she wouldn't hesitate to go on into the danger zone. But is it right for them to ask her to? Kyrano says both he and his daughter owe their lives to him, so for this reason, it is right. Tin-Tin will go with his sons.

Virgil then contacts the island, and says they've just crossed the Himalayan Mountains. They will be touching down on Mount Arkon is about 3 and a half minutes. Jeff asks what it's like out there, and Virgil says it's pretty stormy. Thunderbird 2 is covered in snow, but Virgil is still able to land it.

Virgil contacts Tracy Island and says they've touched down just under the summit of Mount Arkon, and are about to get out the transmitter truck. He asks what the news is from Thunderbird 3. Jeff tells him it's not very good. Their first safety beam projection was a failure, and they're having to go nearer the sun. Virgil tells him not to worry, as maybe they'll have more success this end. Thunderbird 2 then rises up, as Virgil and Brains head out of the pod in the transmitter truck.

The transmitter truck struggles through the snow, but eventually gets to where it needs to be. Brains says this should be fine, as they're well clear of Thunderbird 2. Virgil says they'll start lining up the transmitter beam. The satellite dish on the truck starts to move, and points upwards.

In Thunderbird 3, Alan tells Tin-Tin they're at the first estimated region. If she just gives the word, they'll put her in a release capsule and get her to safety. Tin-Tin says they've been through the whole question, any delay increases the danger to the solarnauts, so she's going with them. Alan says to try the safety beam again. Tin-Tin operates it, and whilst the beam gets further than before, it's still not enough.

Scott says this is what he was afraid of -it's another 2 hours before they're in range. Alan says another 2 hours it is, and hopes they can all stand up to the heat. Meanwhile, Virgil hopes they can stand up to the cold. Brains says they're all set, and activates the truck's safety beam.

He monitors the beam, and says that whilst it's a very powerful beam they're sending up, it's not yet powerful enough. Virgil asks if there's anything they can do, and Brains says that once he modifies the tripartite transistor packs and makes a few adjustments to the wiring, they can try again. Virgil says whilst he's doing that, he'll get them some hot coffee.

Parts of the Sun Probe are starting to crack up. Harris says he can't stand the heat, it's so hot. Camp asks if he can get any more out of the refrigeration plant, but Harris says no -nothing is working any more. Camp wants to know where that rescue ship is, as it has been almost four hours since they made contact with them. In Thunderbird 3, Alan says they dare not to go much closer, as the hull won't stand much more. He asks Tin-Tin to try the signal again.

Tin-Tin doesn't respond at first, but after Alan repeats himself, she does. The beam still doesn't make it to the Sun Probe. Alan asks if Tin-Tin if she can increase the power, and she says she can overrun the system to about point 5. Alan says to do it, as they just can't get any closer. Tin-Tin boosts the power to the safety beam.

The beam finally reaches the Sun Probe, and its retros fire. Harris thinks this is it, the ship is breaking up. He thought he'd be dead before it happened, but it won't be long now. But he then wonders why the module isn't melting, and realizes the noise he can hear... it's the rocket motors -they've fired!

The Sun Probe turns around, and starts to head back to Earth. Harris tells the others they're leaving the sun, they're going to live! Alan says the solar ship is out of danger, so they can head for home. Scott says he couldn't stand much more of this heat. Alan tries to fire Thunderbird 3's retros.

However, the retros don't work, and now Thunderbird 3 is on a collision course with the sun! On Earth, Eddie reports that they're certain the solar spaceship has been saved. He starts thanking International Rescue, but then receives more news. According to the tracking stations, Thunderbird 3 has not altered course, and is heading straight for the sun. Gordon thinks this retros must have failed, so Jeff says they've got to get through to Brains right away.

Jeff tells Virgil and Brains about what's going on. Virgil asks Brains about what they are going to do. Brains thinks that if Thunderbird 3's beam transmitter is still operating, they could perhaps neutralize the transmitter on Thunderbird 3. He doesn't know the frequency, but he could probably work it out on the mobile computer in Thunderbird 2. On Thunderbird 3, Tin-Tin has collapsed due to the heat.

Scott has also collapsed, and Alan tries to think of why the retros haven't fired. He realizes it could be a lack of power, and it must be the radio beam. He asks Tin-Tin if she's shut down the beam, but gets no response. Meanwhile, Eddie reports that only a specially fitted ship can withstand the heat, and Thunderbird 3 is doomed. In saving the solarnauts, the gallant International Rescue crew have lost their own lives.

Jeff says he won't believe it, Scott, Alan and Tin-Tin have got to get out of it. Virgil and Brains go back to Thunderbird 2, and enter the pod. They get the mobile computer box, and Brains says to open it up so they can work out the formula for the transmitter. But as the box is opened, Braman is inside it! Brains realizes they've brought the wrong box!

Alan uses an elevator to get down to where Tin-Tin is, and says he must reach the control panel. But his vision gets blurry, and he collapsed before he can get near it.

Back on Earth, Brains thinks it's no use, there's nothing they can do. Virgil asks if Brains can work out the formula on paper, but Brains says without a computer, it'd take weeks. Brains then thinks that Braman is their only hope, and switches him on. He tells Braman that he wants him to calculate the following equation: what is the square root to the power of 29 of the trigonometric amplitude of 87 divided by the quantitative hydraxis of 956 to the power of 77? He asks Braman if he understands the question.

Braman says he does, and starts to work out the answer. After several seconds of him clicking and whirring, he says the answer: 45,969. Virgil says it has worked. Brains just hopes that it's right. He tells Virgil that they need to get back to the transmitter truck.

Jeff tries to contact Virgil and Brains, but gets no response. Gordon suggests they used all their power on the safety beam, but Virgil then contacts them. He says they don't have time to explain, but Brains is going to try to jam Thunderbird 3's transmitter. Brains says he's lined the transmitter up, and turns it on. The transmitter truck fires off another beam into space.

This time, the beam is seen reaching its target. As the beam reaches Thunderbird 3, its retros then fire. Thunderbird 3 turns around, and flies away from the sun.

Alan gets up, wondering what's happened. He realizes the retros must have fired, as now they're moving away from the sun! Brains and Virgil get a reading from Thunderbird 3, and know it means the retros have fired. Jeff tells them they've done a great job, and he's really proud of his International Rescue team today. He tells them to head back to base, as they'll give a heroes' welcome to Tin-Tin, Scott and Alan.

Sometime later, Brains says now the excitement of Thunderbird 3's homecoming is over, he wants to see if his improvements to Braman have worked. Braman makes another move on the chessboard, and puts Brains in checkmate. Brains can't believe it -a machine can't have a brain better than his!

Jeff thinks it was a fluke, as Brains has been working kind of hard lately. Brains thinks that must be it, he wasn't concentrating. Jeff thanks for him for all he's done, as do Alan, Tin-Tin and Scott. Braman then also thanks Brains for his work.