A hangar opens up at the Matthews Field Air Force base, revealing an RTL 2 plane. In the control tower, the Commander is told by Scheiler that all security systems are operational, so there shouldn't be a thing to worry about. The Commander says that's what they thought last time, but they were wrong. Scheiler says the plane looks good, but the Commander says the physical contours of the RTL 2 interest him much less than the success of the whole operation. He asks Hitchins if the plane's crew have been given their sealed orders yet, and he says they have.

Inside the plane, the crew read their orders. They start to plot a course, but Captain Savidge decides to contact the Commander first. The Commander tells Savidge that the only danger in this operation can arise if an enemy were to find out where the aircraft is at any given time. He wants him to preserve complete radio silence, so as soon as he's leveled out, he doesn't want to hear another word out of him. He's only to break silence in case of an extreme emergency. He tells him he has his orders, all he needs to do is carry them out -good luck. Savidge says he'll sure be glad when they've delivered this cargo.

In the back of the plane are two large Poseidon rockets. As the plane starts to move down the runway, the radio is on. The presenter says that Radio Maxwell is proud to bring back to the microphone the Cass Carnaby Five, here at Paradise Peaks. The band start playing their chart topping hit, Dangerous Game. The plane takes off and leaves the base.

At Tracy Island, everybody is listening to Dangerous Game. Thunderbird 3 is currently docked in Thunderbird 5, and the radio is playing Dangerous Game there too. Alan says he hope's Tin-Tin is listening, as she really digs this number. John thinks it's a great tune, but then he and Alan hear an emergency call from RTL 2.

The staff at the base answer the call. Savidge reports that they are under attack! There are three fighters which have some kind of oval markings on them. The jets then start firing missiles at the plane, which gets hit twice. Savidge reports they can't stand up to much more of this punishment, but then the radio goes dead.

Hitchins managed to get a fix on the plane's position, so several relief aircraft take off. The Commander says that this is the third time this has happened... the third time! The back end of the RTL 2 has caught fire, and the plane goes down in flames.

Alan has returned to Tracy Island. He wonders if it was a coincidence. Tin-Tin asks what he's talking about, and he says Dangerous Game -just before that transporter crashed, that tune was being played on Radio Maxwell. Scott asks what's so unusual about that, they must have played that tune a million times on the radio in the past month. Alan says it was being played on Radio Maxwell before the other two transporters crashed too. Jeff asks what he's getting at, and he says each time they were attacked, the Cass Carnaby Five have been giving a live performance of Dangerous Game. Tin-Tin thinks surely that band could have nothing to do with this this business. Jeff thinks there could be a connection, and asks where that band is now.

Virgil says right now the band is doing a season at Paradise Peaks. Scott says that's the super deluxe hotel high up in the Alps. Jeff asks Brains what he thinks. Brains says it's certainly an interesting observation that Alan has made, so he'll get John to radio them a recording of the broadcast. Jeff says in the meantime, they'll investigate the hotel, and he knows just who to send there. In England, Penelope tells Parker what a lovely day it is. Parker asks if he could have the rest of the afternoon off, and Penelope lets him.

As Parker leaves, Penelope then gets a call from Jeff. Jeff says he's organizing an investigation into the crashing of those rocket transporters, and needs her assistance. He wants her to go to Switzerland and go to the Paradise Peaks hotel, to investigate the Cass Carnaby Five. Inside the mansion, Parker is getting ready to impress Lil with his new suit. But he then gets a call from Penelope, who tells him they're off on a mission.

She says this time it's show business, and she believes he has connections in the theatre world. Parker says he has excellent connections. He heads off to International Artistes Management Ltd, to see Maxie. Maxie wants to know who the heck Wanda Lamour is. Parker says she's by way of being a very provocative torch singer. Maxie says he's really love to do him a favor for old time's sake, but he runs a big agency here. He can't send a singer out to Paradise Peaks that he's never heard of! Parker says that's a real pity. He was in the States last week, and he was only saying to "Punchy" Patterson...

When Maxie hears that name, he gets anxious. He says he'd heard Patterson was inside. Parker says a bloke like Punchy wouldn't stay behind bars with his muscles. Maxie asks Parker if he told Punchy where he was. Parker says he didn't know what to do, as Punchy was in a very anxious state, and kept going on about some unfinished business. Maxie says he gets the message, so he'll make a deal with him. He'll have this Wanda Lamour sent to Paradise Peaks in exchange for Parker keeping his mouth shut.

Penelope is Wanda Lamour, and she looks at herself in a mirror. She thinks this ought to do the trick, but then Parker knocks on the door. He mistakes her for someone other than Penelope, so Penelope says it looks like her disguise is a success, so she should go down well. Parker says that if you go down well at Paradise Peaks, you'll go down well anywhere. Meanwhile, at Tracy Island, a jet is preparing to take off.

Alan contacts Tin-Tin and tells her she's clear to go, so she takes off and leaves the island. Penelope contacts Jeff and says that her flight will be departing in ten minutes. Jeff tells her that there haven't been any new developments, but Brains is working full time on the Cass Carnaby recording. He's exploring the possibilities for melodic patterns causing mechanical changes in the aircraft. It has been established that a radio was playing in the aircraft at the time of the last disaster.

In the lab, Brains explains to Alan that repeated melodic patterns from the Cass Carnaby group could be used to impede the efficiency of the aircraft. Alan says that the transporters each time reported that they were under attack, it was the fighters that shot them down. Brains says that's true, but perhaps the music was affecting their ability to retaliate. He does think that what Alan said about there being something in the music is true, like a musical code. Alan says they'd better try to decode it, as Penelope and Tin-Tin will be arriving at the hotel soon, and will need all the help they can give them. Meanwhile, a cable car moves up towards the hotel.

Tin-Tin says they weren't joking when they said this is the highest hotel in Europe. Penelope says she feels rather lost without Parker, and is beginning to wish they'd taken the Rolls with them. Tin-Tin reminds her of what they'd been told about the long, dangerous road below. Penelope thinks maybe it's just her disguise that's making her nervous. Tin-Tin tells her to cheer up, as she'll be alright -provided they don't ask her to sing. Penelope says she's going to plead a little throat trouble. They then see the Paradise Peaks hotel.

That night, the Cass Carnaby Five are playing Dangerous Game. Penelope and Tin-Tin are in the audience, but Tin-Tin can't believe the band have anything to do with the sabotage. As the song finishes, Cass thanks everyone for the applause. He then tells everyone to say hello to their next guest star here at the Peaks. He would ask her to sing, but unfortunately her opening has been postponed because of an infection in her pretty little throat.

The spotlight is put on Miss Wanda Lamour. Later on, Cass thinks it was nice of Tin-Tin to come round and see him like this and asks when she got here. Tin-Tin says just today, she came here with Wanda Lamour. She says she must have heard Dangerous Game a million times, but it still knocks her cold every time she hears it. Cass thanks her and tells her she's a bit of a knockout herself.

Tin-Tin asks if he gets tired of playing that tune, and if he ever wants to vary it, like changing the tempo. Cass says they leave that to Mr. Olsen. Olsen, the band's manager, says he has things to attend to. He says he has a couple of points to raise with Cass. As he leaves the room, Tin-Tin asks of Olsen is the band's musical arranger. Cass says he is, and he's a funny guy, but he sure knows the business. Tin-Tin asks what he means by funny. Cass says temperamental would be a better word for it, as he will sometimes make a last minute change just before they go on the air. It drives them crazy, but Olsen does know the business.

Olsen dances with Penelope. He says it's certainly funny that he hasn't crossed paths with Wanda Lamour before, as he knows most of the warblers in show business. Penelope claims to have been around, as high society keeps her pretty busy. Olsen tells her she's still a lady of mystery, as she's told him everything and nothing -she intrigues him. Penelope wants to know more about him, as she hears he keeps the Cass Carnaby boys on their toes. Olsen asks her what else she's heard, and she says that he also is a mystery. She asks what his secret is, but he asks to what -of his success, or his good looks? Penelope says both. As the tune ends, Olsen says plenty of beauty sleep, but then says that's his cue to excuse himself from her very charming company.

As he leaves, Penelope hears someone trying to get her attention. She sees Parker at the bar, who explains that he got a job as a part time bouncer. Penelope says they seem to be having very little success, she'd really enjoy one of his splendid cups of tea now. Parker tells her he'll send some up at once. Later on, Parker brings the tea to Penelope and Tin-Tin. Parker says he overhead Olsen talking to Banino, the headwaiter, about expecting a message tomorrow morning. Penelope asks where Olsen lives, and Parker says in a chalet round the other side of the mountain. Penelope thinks they ought to follow this up at once, and she believes Olsen will soon find out she's a fake.

Tin-Tin says they'll report to Jeff, and calls International Rescue via radio. In the lab, Brains is playing the recording again. He tells Jeff that he's definitely established that there's some kind of electronic pattern in the music. Jeff asks if really means the music was used as a code, and Brains says it looks quite likely. But he'll still have to decode the music before he's sure there's a code in it.

Tin-Tin then reports in and says they feel that Olsen, the music arranger, could be the man they're looking for. But what they don't know is if he's working alone or if all the group are involved. Jeff says that Brains is pretty certain that the music has some kind of hidden meaning. He asks Tin-Tin if they need any help, but she says not yet. They'll let him know more definitely tomorrow, after they've called on Olsen. The next morning, Penelope and Tin-Tin leave the hotel.

They ski to towards Olsen's home, and Penelope says they're nearly there. At Olsen's home, Olsen is playing the piano, but he stops when he hears an alarm buzzing.

Penelope and Tin-Tin arrive just in time to see Olsen sit down at a machine. As they hide behind some trees, Penelope wonders what it is Olsen's working at, and Tin-Tin thinks it's some kind of electronic computer. She reveals a camera hidden in one of her ski poles, and uses it to start recording Olsen.

The computer displays a code on the screen, which doesn't make any sense. But as Olsen continues to operate, the code changes to English text, which states the exact time the next rocket transporter is to depart, and that its destruction is imperative! Realizing that Olsen has just been giving his orders for the next sabotage operation, Penelope and Tin-Tin leave so they can warn Jeff.

As Olsen leaves the computer, he sees some tracks in the snow nearby. He uses a telescope and sees Penelope and Tin-Tin skiing away from his home. He quickly gets on the phone to Banino. At the hotel, Parker overhears Banino talking to someone about that singer no one has ever heard of. He then says he'll deal with them.

Tin-Tin and Penelope turn on their ski thrusts, which are packs on their backs which give them a momentum boost. But as they ski up the mountain, someone takes aim at them with a rifle: Banino! Parker has been hiding in his car and stops him just as he fires, causing him to miss his shot. The sound of the gunshot echoes across the mountain.

Tin-Tin and Penelope stop and see the car up above them. Parker tackles Banino out of the car, and the two roll down the mountain, become a big snowball that's heading towards Tin-Tin and Penelope. Penelope doesn't think this would be doing Parker's vertigo any good.

The snowball crashes and breaks apart. Parker apologies for the unconventional entrance, but he had to apprehend Banino somehow. That bullet was meant for them, and it means the masquerade is over. Banino had been ordered to dispose of them both. Penelope says they must get back to the hotel and contact Jeff. Tin-Tin says they'll need to hide Banino too. Parker thinks the broom cupboard would be the best place, as when he comes to, they should be a long way from here.

Grandma says she just can't get Brains and Alan to eat anything today, they say they haven't got time. Jeff says those two have just got to get the combination of this code cracked. Penelope then contacts them and says they've traced the men who'd been sabotaging the transporter planes. Jeff tells Brains to get up here right away.

He tells Penelope they've got to work fast. Tin-Tin has her recording played, which shows Olsen using the computer to translate the message. Brains takes a look and says that's it! He can't believe he didn't think of this before: it's a cham-cham! Nobody knows what the means, so Virgil asks him what a cham-cham is.

Brains explains that a cham-cham is a new electronic machine that is sensitive to ultrasonic harmonics and micro tones. Now that he knows the technique they've been using, he'll soon break their code. Jeff tells him to go back to the lab to work on the code, and tells Penelope that she and Tin-Tin need to standby for his next message. He tells Scott to get him Washington DC, as they've got to save that next transporter aircraft. But at Matthews Field, the next RTL 2 leaves the hangar.

Having received a call, Scheiler tries to explain that they can trust International Rescue. But the Commander says if they paid attention to every nut who telephoned in claiming to be International Rescue they'd never get any work done! Scheiler says that Washington thinks they were the real thing. The Commander says he's in charge, and he doesn't intend to make his unit the laughing stock of the US Air Force just because some coot wants to play musical chairs! At Tracy Island, Jeff tells Alan that the Commander at Matthews Field wasn't convinced they were on the level. Alan says Brains has cracked the code and has also calculated how the tune should be altered so that Olsen's message gets changed. Jeff says from here on in it's up to Penelope and Tin-Tin, only they can save that aircraft from destruction.

At the hotel, Olsen tells Cass to try the tune this way tonight, which has a few minor modifications. Cass says he doesn't see what the point it. Olsen reminds him that when they drew up that contract, he agreed to do it his way. Cass says they'll change the arrangement for broadcast. Olsen tells him to let the rest of the band know, as they're on in five minutes. As he leaves, Tin-Tin appears from behind the door. She tells Cass that if he must alter the arrangement, he must change it to their way. Cass says he'd do it if she'd asked him to, but he wants to know why. Tin-Tin says she can't tell him how she came to be involved in all this, he just has to trust her. Cass says this season at the Peaks is the biggest break he'll ever get, he can't break his contract -he's got to do as Mr. Olsen says.

Jeff tells Scott that he hopes this gamble will pay off. It's a desperate step he's getting him to take, but it's the only way to prove to the Air Force that they're in dead earnest. Scott then takes off in Thunderbird 1 and heads to Matthews Field. Jeff tells Alan and Virgil that it's nearly time for the broadcast, and asks Brains if he's ready.

Brains says he is, and has told Penelope how to alter the arrangement to divert those enemy fighters. He just hopes they can persuade Cass Carnaby to play it that way instead of Olsen's way. At Paradise Peaks, the Cass Carnaby Five are about to start playing. Tin-Tin tells Parker that only Penelope can save them now, but Parker wonders where Olsen has got to. The band begin to play Dangerous Game.

At the enemy base, the Commander and his lieutenant hear the broadcast of Dangerous Game. The Commander says their contact at the hotel has a message for them. The lieutenant says he's getting a direction on the flight path of the transporter craft. Three jets move out onto a runway and prepare to take off. But back at the hotel, the tune suddenly changes when Penelope joins the band on stage and starts singing.

Brains says Penelope has done it, the key to the tune is changing, meaning the code is going to change too. At the base, the lieutenant says the message is changing. He reads out the new coordinates, so the Commander tells his pilots to intercept the transporter craft. He gives them the new coordinates and tells them to intercept and destroy the transporter craft.

As Penelope continues to sing, Parker and Tin-Tin then see Olsen waiting around nearby. The song then ends, so Jeff tells Virgil and Alan to get over to Paradise Peaks. He thinks Penelope and Tin-Tin could be in great danger. Virgil and Alan take off in Thunderbird 2.

At Matthews Field, Scheiler says they've just received a request for permission to land... from International Rescue! Scott arrives in Thunderbird 1 and lands in the base. He says a short time ago they tried to tell them their transporter craft was about to be destroyed by enemy fighters, but they wouldn't listen. He's here to inform them that the enemy fighters have now been diverted to over fly the outskirts of this airfield.

Scheiler says those must be the three unidentified aircraft that they just received a report about. The Commander then sees the three jets and notices the oval markings on them. He believes them to be the same jets Savidge reported before his radio went dead. He calls for action stations, as those aircraft must be destroyed! As Scheiler raises the alarm, the Commander begrudgingly says that International Rescue have done it again.

At the hotel, Penelope, Parker and Tin-Tin leave via a cable car. Penelope says she feels dreadful slipping away like this -they haven't even paid their bill! Tin-Tin says it's the only way to avoid Olsen, but Penelope wonders where he could be. At the cable car station, Olsen has seen them leave and is happy they are all in the same car. He says he'll make sure they won't interrupt any more broadcasts, and switches the power off.

The cable car suddenly comes to an abrupt stop. Penelope tells Parker to press the alarm bell, so he does. At the hotel, the noise of the alarm wakes Cass up, who knows that was the cable car alarm.

Olsen starts burning through some cables. The group in the cable car hear the sound of something snapping. Penelope says she doesn't like this at all, and contacts International Rescue. She tells Jeff that it looks like Olsen is going to get his revenge after all. Jeff tells her that Virgil should arrive at Paradise Peaks in two minutes, and asks what the problem is.

Jeff tells Virgil and Alan what's happening. Alan says they should be sighting the hotel any moment now. Olsen continues to cut through the last cable, but Cass sees him and manages to get him away. However the last cable then snaps, which makes the cable car start to rapidly descend down the mountain.

Thunderbird 2 arrives just as this has happened. Virgil puts Thunderbird 2 into a dive, going after the cable car. He tells Alan he'll get close down on top of that car, and when he gives the command, he wants him to fire the magnetic grabs. Thunderbird 2 gets very close to the cable car, so Virgil tells Alan to fire.

The magnetic grabs are fired and hit the cable car, but they fail to stay attached to it. Alan says they just won't hold. Virgil contacts Penelope and asks to speak to Parker -he hopes Parker has a good head for heights. Parker opens the cable car door and climbs up onto its roof.

Thunderbird 2 then lowers down a cable, which Parker attempts to grab onto. But the cable keeps flailing around and he can't catch it. Penelope sees that and tells him to use this -her umbrella. She passes it up to him.

Parker uses the umbrella's handle to catch onto the cable, which he then attaches to the cable car. More cables are then lowered from Thunderbird 2, and Parker manages to attach three of them onto the cable car. But as he tries to get the fourth one, Alan says he's not going to make it in time! Parker manages to get the last cable attached.

Thunderbird 2 then fires its retros, which bring the cable car to an eventually stop. But as it does, Parker gets sent flying off it! The cable car has stopped just meters away from the terminal.

Penelope asks Parker if he's alright, but gets no response. She wonders what could have happened to him, but Tin-Tin points out he's in the sky! Parker uses the umbrella to float down to the ground. Later on, almost everyone has returned to Paradise Peaks.

Penelope tells Virgil it's nice to know Dangerous Game can't be used for any sinister purposes any more. Virgil asks if the hotel people know they're from International Rescue. Penelope says no, but Cass is pretty intrigued about how they knew about the code. Cass is at the piano and asks where Tin-Tin got to, as he hasn't seen her since the last dance. Penelope says that she thinks Tin-Tin and Alan went out for some air.

Cass says Tin-Tin is off home again tomorrow... that's show business. Outside, Alan asks Tin-Tin if she's all cut up about going back to the base tomorrow and leaving Cass and the band. Tin-Tin says she's getting quite used to this hello and goodbye all the time, but it's always nice to get home again.