At his temple, the Hood thinks about International Rescue. He has found out its members now seek further glory in the hunting of ancient treasures. But this time, they will fail! He goes up to his statue of Kyrano, and says the treasure International Rescue seeks will be his. They and their expedition will be buried at the bottom of Lake Anasta. He tells Kyrano that he will help him. He starts calling out Kyrano's name.

In the Tracy Island kitchen, Kyrano suddenly collapses. The Hood tells him it's useless to resist his power, and tells him to speak. He wants to know when the International Rescue expedition will set off. Kyrano eventually tells him that they are leaving tomorrow to make a survey of the temple.

Meanwhile, Scott tells Tin-Tin not to forget to get him a gem or two. Tin-Tin asks John what he wants, maybe a diamond? John says he'd rather have a dirty old bar of gold. Jeff asks Brains if he really thinks they'll find buried treasure down there. Brains says he sure thinks so, he's 90% certain that there's something at the bottom of that lake. Scott thinks it's as good as excuse for any to have a vacation. Kyrano then appears, and says everything is ready.

Tin-Tin and Brains board Thunderbird 2, which takes off. Jeff and Kyrano watch the launch, and Jeff tells Kyrano it'll just be 10 short days until his daughter returns. Kyrano says that's what he keeps telling himself, but he can't shake off these fears. Jeff tells him there's nothing to fear, as it's a beautiful lake miles and miles from anywhere -what could be safer?

The Hood drives his truck through the desert, complaining about how there is nothing but sand here. He wonders how much further it is to the lake, but as the truck drives up a dune, he sees the lake nearby.

In Thunderbird 2, Tin-Tin tells Brains she can see some pyramids. She says they're nearly at the rendezvous, and Virgil says they're well up to time, too. Tin-Tin asks what Professor Blakely is like. Brains says that from what he's heard, Blakely is quite a character, and the best man in his field.

Virgil says that when he gets down there and drops the pod, they'll have to move fast. They mustn't let the professor know they're connected with International Rescue in any way. Tin-Tin says that if Blakely asks, they'll say they got to the Middle East via charter flight. She and Brains then move to the pod, as Thunderbird 2 comes in to land. Virgil then raises Thunderbird 2 up, as the pod door opens.

Brains and Tin-Tin leave in their vehicle, which is pulling two caravan trailers along with it. Thunderbird 2 collects the pod and immediately takes off again. Brains hopes their secret landing passed off kind of secretly. Now they need to meet up with Blakely, and Tin-Tin says the professor should be at the crossroads three miles along this road.

The professor is on his way, using Hassan Ali's luxury taxi service. Brains and Tin-Tin arrive at their destination, and Tin-Tin says how cool it is in here. Brains says its got to be, as the temperatures can get up to 112 in the shade. They then hear the sound of a car engine misfiring, and find that the professor has arrived.

Brains introduces Blakely to Tin-Tin and then asks him what he wants to do first. Blakely says they could pop down to the lake, but he needs to pay off this cabbie first. He pays the taxi driver, who then drives off.

Brains asks Blakely if he'd like a cooling drink before they set off. Blakely says yes, stating the treasure can wait -he doesn't think anyone is going to steal it from under their noses. But at the lake, the Hood backs his truck up and then has it open up, revealing a small submarine. The submarine is sent down a ramp, and hits the water. The Hood then drives his truck away from the lake.

Brains and the others head to the lake. Tin-Tin sees the Anasta pipeline, and says that the lake must be quite near. Blakely says that with a bit of luck, they can look at the temple before nightfall. Brains says they'll do just that, as they arrive at the lake. In the lake, the Hood has entered his submarine, and uses its periscope.

He says that his friends are just in time... in fact, they're dead on time. Brains, Tin-Tin and Blakely set up their camp at the edge of the lake. Brains tells Blakely that he and Tin-Tin are going to take their first look at the temple. Tin-Tin says they'll be the first people to set eyes on the temple in over 100 years.

Blakely tells them that 100 years might have effected the stone work, so they need to be careful when they're down there, as it could be treacherous. Brains and Tin-Tin enter the lake, and swim down to where the temple is. Brains tells Tin-Tin to be very careful, as Professor Blakely was right -this temple doesn't look too solid.

Meanwhile, the Hood moves his submarine closer to the temple. He sees Brains and Tin-Tin, and says they're going to lead him straight to the treasure. Brains and Tin-Tin enter the temple, but Brains says the problem is which column would contain the treasure? Tin-Tin decides on which one they should try, so they swim over to it.

Brains thinks this could be the one, so Tin-Tin says they should take a sample back to the professor. Brains chips away at the column and breaks a small chunk of rock off from it. He contacts Blakely and says he's going to bring him up a sample from the central column. Blakely says to bring it up so they can have a look at it before lights out. Brains and Tin-Tin leave the temple and swim up back to the surface.

The Hood sees them leave, and believes that they've found the treasure. He wonders where the treasure is, but thinks he can persuade them to tell him. Meanwhile, Brains and Tin-Tin return to their camp. Brains examines the sample and breaks another piece of it off. Blakely looks at it and tells them that the expedition is a success: they've located the lost treasure. Tin-Tin says they must radio Jeff and tell him.

That night, Brains examines part of the sample. He says he always knew that his theory was correct, and tomorrow he can collect lots more evidence. He then hears someone knocking at the door, and goes to answer it. But when he opens it, he sees a man there he's never seen before. He asks him who he is and what he wants.

The man's eyes start glowing. Brains asks him again who he is, but then he falls down. The man removes a mask, revealing that he is the Hood.

The next morning, Scott says that Brains radioed in last night to tell them they'd traced the lost treasure. He reported in before turning in for the night, and he and Tin-Tin had been down to the underwater temple as soon as they got there. Jeff says they should be coming in with their next routine contact call soon, so he'll convey them their congratulations then. Grandma Tracy wonders what Tin-Tin wanted to go hunting that treasure for, as she's got enough jewelry already. Scott explains they aren't going to that temple to rob it, it's all in the interest of science. Whatever they found is going back with Professor Blakely to the International Museum of Archaeology.

Jeff says he's going back to lounge to wait for the next call from Brains. He thinks the group must be feeling pleased with themselves, but at the camp site, Brains has been buried in sand. He wakes up and asks Tin-Tin what happened, but realizes neither she or the professor are here. He recalls the stranger with those staring eyes, but then realizes how thirsty he is. He can see the camp a short distance away.

In one of the trailers, Tin-Tin is in a trance, not moving. In the other trailer, the professor has been beaten up. Brains says it's no use, but if only he could get to the radio. A voice asks him what he would do then -inform his friends at International Rescue?

The Hood is back in his disguise, and he tells Brains that's out of the question. Brains asks what he's done with the others, but the Hood tells him he'll deal with them later. First, he wants some information from him -where is the treasure concealed in the underwater temple? Brains asks for water, he's got to have some.

The Hood tells him to answer his question. He saw him leave the temple with some of the treasure, so where is the rest of it? Brains tells him he doesn't know who he is, but he wants some water. The Hood says to say where the treasure is, then he'll let him and his friends go -it is a simple choice to make. But Brains then passes out. At Tracy Island, Jeff hasn't heard from Brains, which is surprising since he's never been late before. He tries again, but gets no reply. He tells Kyrano to get and get Scott.

Jeff tries again, but there is still no answer. Scott comes in and asks what's up, as Kyrano seemed to think there was something wrong at the lake. Jeff says Brains hasn't checked in yet, and he's overdue by 14 minutes. Scott says Brains seemed in great spirits last night. Jeff says he's tried both channels, but there's nothing on either. But they then hear an alarm start buzzing, and Jeff says it's the emergency signal. Jeff tells Scott he'd better get out there fast.

Scott takes off in Thunderbird 1. Jeff tells Scott that Virgil will be following him, so he is to proceed at maximum speed. A short time later, Thunderbird 2 also takes off, carrying pod 4.

Back at the lake, Brains wakes up again. The Hood has returned to his submarine, and decides to check on Brains again in 9 more minutes. He believes no man can stay in the burning sun for long without having his tongue loosened. He uses his submarine's periscope and sees Thunderbird 1.

Scott tells Jeff he's flying over the danger zone, but it all looks very quiet to him, perhaps too quiet. Jeff asks if there is any signs of life. Scott says the caravans are there at the edge of the lake, but he can see no sign of Brains or Tin-Tin. Jeff tells Scott, Virgil and Gordon that he wants tri-circuit contact maintained at all times. Virgil says his eta is 2.5 minutes.

Scott then says he can see Brains down below, buried in the sand up to his neck! He says he's going down now, so he lands Thunderbird 1. This is seen by the Hood, who thinks they've found his victim in the sand. But he can turn this setback to his advantage, as now he has the chance to destroy International Rescue utterly after they've led him to the treasure.

Scott goes to Brains, who is asking for water. Scott asks who did this to him, but Brains asks where Tin-Tin is. Scott says he doesn't know, but they'll soon find her. But first he's going to get him out of here. The Hood then sees Thunderbird 2 coming in to land, and thinks this is a veritable swarm of Thunderbirds. He says this is for the first part of his plan, and flips a switch on one of the consoles to start recording footage of them.

The automatic camera detector in Thunderbird 1 goes off, but as Scott is outside it goes unnoticed. Scott and Gordon get Brains out of the sand, and Scott asks how he feels. Brains says he feels alright, but asks about Tin-Tin. Gordon says she's going to be ok, but the professor is not so good. Meanwhile, Virgil finds Tin-Tin and asks about what happened. She says there was a stranger, who had terrible eyes she couldn't look away from. She's never seen the man before in her life, yet she felt she knew him in some far off way.

Scott reports back to base. Jeff says he wants all International Rescue members to come straight back to base in the morning, as soon as the helicopter has taken care of Blakely. Scott asks about the expedition, and Jeff tells him that the treasure at the bottom of the lake will have to wait. International Rescue isn't setup to go joyriding around on treasure trails. The others have gone into one of the caravans. Brains says he feels a lot better now, and asks how the professor is. Gordon says he's still unconscious, but guesses he's going to be ok.

Scott then returns and says that his father is arranged for a helicopter to ship out the professor to a hospital, then they've got to hotfoot it back to base. But one thing puzzles him, he noticed that the photo alert in Thunderbird 1 had been operating. Gordon thinks that's impossible, as who could be taking photographs of Thunderbird in this area? Brains thinks that's it -this whole expedition has been used be their enemies as a means of drawing International Rescue to a lonely spot. They've walked straight into a trap!

Later on, Brains wakes Tin-Tin up and tells her he can't sleep for worry. Tin-Tin asks what he's worried about, and he reminds her about what Mr. Tracy said about the Anasta expedition causing a lot of trouble. Tin-Tin didn't think he meant they'd done it deliberately, but Brains says he feels awfully guilty about it. And to cap it all, they've got someone spying on them. He thinks there is only one place the guy could be observing them from: the center of the lake. Brains wants to try and make amends for all the trouble he's caused, so he's going to go and see what's down in the lake. He wants her to keep in touch with him via the talk back radio. Tin-Tin says she will, but she doesn't like it.

Brains swims down to the temple. He inspects the column and breaks part of it off, revealing some treasure inside it. He tells Tin-Tin that they had found the right column, but she asks him if there is anyone down there. Brains says no, there appears to be no one down here. But he then finds something odd on the ground: a cable.

When Brains touches the cable, it sets off an alarm which alerts the Hood. He says he has visitors, and his little alarm system works. Brains tells Tin-Tin he thinks he's onto something, as e's found a cable leading from the column. He then says he's found another one, but Tin-Tin says she's going to wake up Scott and the others. Brains tells her there's no need for that yet. But the Hood then leaves his submarine.

Brains continues to follow one of the cables, but he soon finds the Hood. The Hood's eyes start glowing again, and Tin-Tin hears Brains says something about those eyes.

She hears Brains say those staring eyes, but then contact is lost. Brains has collapsed, so the Hood swims away from the temple. Tin-Tin wakes the others up and says she tried to stop Brains, but he wouldn't listen. Virgil tells the others to come on, as they've got to get down there right away.

The Hood has returned to his submarine, and says he must get the treasure before Brains' friends find him. He detonates some explosives he'd set in the temple, causing large chunks of the structure to fall apart. Some of the debris covers up Brains.

Next to the lake, Thunderbird 2 rises up, revealing pod 4. The pod door opens, as Gordon says he's commencing launch. Thunderbird 4 leaves the pod, and enters the lake. Gordon arrives at the temple and reports to Scott that it is in ruins. He doesn't thinks Brains could have survived.

Scott tells Gordon to search the area, as if he is alive, he's got about seven minute of oxygen left. Gordon says there isn't a sign of him, he'll try again but it doesn't look too good. Scott says that Brains has around five and a half minutes of oxygen left. As Thunderbird 4 continues to move around the temple's ruins, the Hood moves his own submarine into position.

Gordon then tells Scott he can see some air bubbles coming up from some rubble. He asks him to hurry and bring the aerostatic lifting kit, as it could be Brains. Gordon tells Virgil he's going to start clearing. Meanwhile, the Hood says that now he'll destroy International Rescue, and collect the treasure.

The Hood fires two missiles, one of which hits a pillar, the other of which hits the back of Thunderbird 4. Gordon says he's being attacked, and tells Virgil to stop Scott from coming down here yet. The Hood turns his submarine around and starts to move away from the temple.

Gordon manages to turn Thunderbird 4 around and chases after the other sub. He fires a missile at it which hits it on the backside. The Hood realizes that his submarine is flooding in the motors section, causing it to dive and crash at the bottom of the lake.

He gets out, moments before his submarine explodes. The explosion is so large Virgil and Tin-Tin see it on the surface of the lake. Virgil asks Gordon what happened, but Gordon says that he'll explain later.

Gordon tells Virgil to get Scott down here fast. He then leaves Thunderbird 4 and heads to the place where he saw the air bubbles. Scott then comes down with the aerostatic lifting kit.

Virgil asks Tin-Tin to go and make sure the professor is comfortable, as the helicopter is due in three minutes. Virgil then asks Gordon how it's going. Gordon says Brains found his treasure alright -they're swimming in it! They're going to release the lifting kit now. The kit is activated, which deploys a large balloon. The balloon has been tied to a pillar that Brains is trapped under. The balloon starts to pull the pillar up, allowing Gordon to pulls Brains out of the way.

He does this just in time, as the rope around the balloon's hook snaps and causes the pillar to drop back down. A few minutes later, the helijet departs from the camp, taking Blakely away.

Tin-Tin hopes the professor understands, so Virgil asks her what she means. Tin-Tin thinks it looks a bit heartless shipping him out like this, just so he doesn't realize that she and Brains belong to the International Rescue team. Virgil thinks the best thing for the professor in his condition is hospitalization -but he'll sure get a surprise when he comes to. Later on, Brains and Tin-Tin visit the professor. He says it was jolly nice of them to look him up like this. Tin-Tin says that now the world has heard about their discoveries at the lake, she asks the professor what it feels like to be a celebrity? He says pretty fair, but asks how they're fixed over the next few months. Brains asks why, and the professor says he's been reading about some treasure in the Caribbean from 400 years ago. He thought they might be interested in taking a trip out there to have a look. Brains and Tin-Tin decide to leave.

Blakely asks what the hurry is, so Tin-Tin tells him visiting hours are over, so they've got to go. They leave, and the Blakely thinks the excitement must have been too much for them. Tin-Tin tells Brains is what they need is a nice, quiet rescue to soothe their nerves. As she tells Brains they need to get back to base, Blakely resumes reading his book: Treasure - The Easy Way.