The Commander tells the Captain that once he is in the air, he is to maintain total radio silence until he lands at his destination. He should only break the silence in the case of an extreme emergency. Captain Savidge says he'll be glad when they deliver their cargo, which is two large and highly powerful missiles. As the plane starts to take off, one of the crew has his radio on. A song from the Cass Carnaby Five, live at Paradise Peaks Hotel, begins to play.
The RTL2 takes off without any problems. The Cass Carnaby Five song, "Dangerous Game" is an international hit, and on Tracy Island, the whole family is listening to it. Even in space the song is on, as John and Alan have it on in Thunderbird 5. However, they then hear an emergency call, from the crew of the RTL2 jet.
The crew call back to the control tower, and say they are under attack from three enemy fighter jets with oval markings. The Commander says this is the third time this has happened, but then contact with the RTL2 jet is lost. Badly damaged, the jet goes into a dive and crashes.
Later on, Alan has returned to Tracy Island, and asks Tin-Tin if it was a coincidence that when the RTL2 jet was shot down, "Dangerous Game" was playing on Radio Maxwell. Scott questions why that is important, as that song must have been broadcast a million times by now. Alan says that "Dangerous Game" happened to be playing live when the previous RTL2 jets crashed also. Brains says he'll have John to send a recording of the song down so he can analyze it. Finding out that the Cass Carnaby Five are currently performing at a deluxe hotel known as Paradise Peaks, Jeff decides to send Penelope to investigate.
Penelope receives the call via her teapot radio, and Jeff explains that he wants her to go to the Alps, where this Paradise Peaks hotel is. Parker is about to have the afternoon off to take Lil the cook out, but Penelope asks for him to get ready -they are going on a mission, and she needs him to use his connections in the theatre world.
Parker goes off to visit an old friend of his called Maxie, who now manages international artistes. Parker wants a singer called Wanda Lamour sent to Paradise Peaks to perform. Maxie is reluctant to send a singer he has never even heard of to somewhere like that, but Parker changes tactics. He mentions that he was in the United States the other week, where he met "Punchy" Patterson. Maxie is alarmed at this as he thought Patterson was in jail, but Parker says a guy as muscular as Punchy was never going to stay behind bars for long. And he told Parker he had some unfinished business. Maxie sees what he is getting at, and makes a deal: he'll have this Wanda Lamour sent to Paradise Peaks, but in return, Parker will keep his mouth shut, so Punchy Patterson doesn't find out where Maxie is.
Later on, Penelope is getting ready; she is going to become Wanda Lamour, and has her disguise prepared. On Tracy Island, Tin-Tin is also going to be going on the mission with Penelope, and leaves on a small jet.
Penelope contacts Tracy Island and tells Jeff her flight is about to depart. She asks if there have been any new developments, and whilst there is no news yet, Jeff tells her Brains is working full time on the song recording John sent him. Brains is telling Alan about repeated melodic patterns in the music could be used to impede the efficiency of the aircraft. Alan points out that each time the jet crews reported in, they stated they were under attack, and did not report they had malfunctions. Brains wonders if the music could contain some kind of code. Alan says they'll have to try and crack it, as Penelope and Tin-Tin will be arriving in the Alps soon, and will need all the help they can get.
Penelope and Tin-Tin take a cable car up to the Paradise Peaks hotel. Penelope says that she is going to pretend to have a sore throat so she won't be asked to perform, meaning she and Tin-Tin can go about their investigation. Later on, the two watch as the Cass Carnaby Five perform "Dangerous Game". Tin-Tin finds it hard to believe that the group would have anything to do with the destruction of the RTL2 jets. As the music finishes, the leader of the band, Cass Carnaby, takes to the mic and introduces the whole room to Wanda Lamour, who cannot perform tonight due to a sore throat.
Backstage, Tin-Tin manages to have a few words with Cass Carnaby. She says she likes the song, but doesn't he ever get tired playing it over and over again? Doesn't he want to vary it? Cass says he leaves stuff like that to Mr. Olsen. Olsen is behind them and after checking his watch, he says he needs to take care of a few things, and needs to have a word with Cas. As he leaves, Cass explains that Olsen is there musical arranger and whilst he knows the business, he can be a bit temperamental -he sometimes makes last minute changes to their music before they perform it.
Later on, everyone is on the dance floor, and Wanda gets to dance with Olsen. He says it is strange their paths have not crossed before, and he knows very little about her. Wanda says that he is also a man of mystery, but as the current tune ends he says he has to leave, and Penelope has not learnt as much as she would have liked. Parker then calls her over -he says he's gotten part time work as a bouncer, as he thought he'd be more use to her up here. Penelope admits that she and Tin-Tin are having very little success. The three regroup in Penelope's room, where Parker says he overheard Olsen talking to Banino, the head waiter, about a message he was expecting. Penelope thinks they should follow it up and finds out Olsen lives around the other side of the mountain.
Back on Tracy Island, Brains is still experimenting with the recording and tells Jeff there is some kind of electronic pattern in the music. The music is looking quite likely to have been used as a code. Jeff then receives a call and asks what is up. Tin-Tin tells him that they have not discovered anything yet, but believe that Olsen could be the man they are looking for. They don't know if he is working alone, or if all of the group are involved. They'll call in again tomorrow after they have visited Olsen's place.
Tin-Tin and Penelope ski to were Olsen's home is, and as they quietly approach, they see Olsen using some kind of computer. Strange symbols appear on the screen. Tin-Tin uses a hidden camera to start filming. The symbols change into English text -stating when the next RTL2 jet is going to take off!
Tin-Tin and Penelope head back to the hotel -but as they do, they leave tracks in the snow. Olsen happens to see them and uses a telescope to see that two people are heading back, so he phones Banino. Banino finds out that the singer nobody has heard of is causing trouble, so he'll deal with her. Parker happens to overhear his conversation.
Banino drives out to part of the mountain, and gets ready so shoot Wanda and her friend. But as he is about to take a shot, Parker charges into him, causing his bullet to miss. Parker grabs him and removes him from his car, as they roll down the mountain.
They get covered in a lot of snow and soon turn into a large snowball, but eventually come to a stop when they roll into a large rock and the snowball breaks on impact. Penelope and Tin-Tin come over, and see that Parker is alright, whilst Banino is unconscious. Penelope says that gun shot they just heard was clearly meant for them. They need to contact Jeff Tracy quickly, so they head back to the hotel. Penelope calls Tracy Island, and shows Jeff the film which Tin-Tin recorded. Brains comes into the lounge to take a look.
Brains realises what this is -it is a cham-cham! He says that a cham-cham is a electronic machine which is sensitive to ultra sonic harmonics and microtones. Now that he knows the technique they've been using, he'll soon break their code. Jeff tells Brains to get to work, whilst Penelope is to wait for his next message. He has Scott get into contact with Washington D.C., as they've got to save that plane. At the air force base at Matthew's Field, the next RTL2 jet is heading towards the runway.
Word reaches Matthew's Field that International Rescue have sent a warning, but the Commander refuses to believe them. He thinks whoever it was who contacted Washington were not really International Rescue, and refuses to stop the RTL2 from taking off. Back on Tracy Island, Jeff says the Commander at the air force base won't listen. Alan says Brains has cracked the code, and has composed an altered version of "Dangerous Game" which will change the message. Jeff says it is up to Penelope and Tin-Tin now -only they can save the RTL2 from destruction.
The RTL2 jet takes off as scheduled. Back at Paradise Peaks, Olsen tells Cass he has changed the tune of "Dangerous Game" slightly, and wants him to play it a different way tonight. Cass questions why he has to keep changing it, but Olsen reminds him of their contract -the band agreed to do things his way. Cass says he'll do it, and Olsen leaves. But Tin-Tin then appears and says that if they are going to change the tune, they need to do it her way. Cass asks why everyone wants to change "Dangerous Game" but Tin-Tin says she can't go into it -he will just have to trust her.
Scott takes off in Thunderbird 1, as Jeff wants him to fly to Matthew's Field to prove that International Rescue really is involved. As he heads off, the Tracy family tune into Radio Maxwell, as the Cass Carnaby Five are about to play. Brains says the arranged version of the tune he made will divert the enemy fighters, but only if Penelope can make the band play it. At the Paradise Peaks hotel, the band start to play "Dangerous Game" but it is at a faster tempo, and one of the band is using a flute rather than a saxophone.
At an enemy base, a Colonel is listening to the music on a radio, but he and his Lieutenant use a computer to get information out of the tune. This information is the flightpath of the RTL2 jet, and the Colonel has three fighter jets prepare for launch.
Back at the hotel, Cass Carnaby and his band continue to play, but then Wanda Lamour comes on and starts to sing. The tune changes, which effects the code. At the enemy base, the Lieutenant says the message is changing, and sees that the co-ordinates have changed. The enemy jet they want to destroy is now at point 629668, so the Colonel tells the three pilots to take off in their jets and shoot down that aircraft.
Wanda continues to sing, but Tin-Tin points out to Parker that Olsen is watching. As the song finishes, Jeff tells Virgil and Alan to get going in Thunderbird 2, as Penelope and the others could be in great danger.
Scott lands in Matthew's Field, and through a loudspeaker, he tells the control tower staff that they tried to warn them about the danger their RTL2 jet was in from an enemy attack, but they did not listen. However they have now diverted these enemy fighters and they are about to fly over the outskirts of this airfield. The control staff had picked up three unidentified jets and realise they must be the enemy fighters, so they dispatch their own jets to shoot them down. The Commander is reluctant to admit that International Rescue have done it again.
Penelope, Parker and Tin-Tin leave Paradise Peaks early in the morning, and whilst they haven't paid their bill, they know they've got to get out of there fast because Olsen will surely want to kill them all. As they head away from the hotel in a cable car, Olsen has seen them leave, and shuts off the power to the cable car system. He then uses a blowtorch to start cutting through the wiring. Penelope contacts Jeff and says they need help, and finds out Thunderbird 2 is already on the way.
Cass happened to hear a cable car alarm go off, and goes into where Olsen is. He tries to stop Olsen from cutting through the cable, but by the time he grabs him, he's done enough and the cable snaps. Thunderbird 2 arrives at the hotel, but Alan points out a cable car, which is rapidly descending down the mountain. The cable must have been cut to make it move so fast.
Virgil moves Thunderbird 2 in, and is soon following the cable car. Alan fires the magnetic grabs, but they won't hold and slide off. Virgil contacts Penelope and tells her that Parker is going to have to help. Parker opens the cable car door and heads up to the roof.
Virgil releases several cables and, using an umbrella Penelope passed up to him, Parker hooks them up to the cable car. He attaches all four of them and Virgil then uses Thunderbird 2's retros. The force of this causes Parker to slide off the cable car! The cable car comes to a safe stop just in time, and Parker has also survived thanks to the umbrella.
Later on, at the Paradise Peaks hotel, Penelope and Virgil are at a table and Virgil asks if the hotel staff will know they are from International Rescue. Penelope says she doesn't think so, although Cass seems quite interesting in knowing how they knew how there was a code, and how they broke it. Cass is playing the piano when he asks where Tin-Tin is. Penelope says that she's outside getting some air with Alan. Cass knows she is going home tomorrow, but then that's show business. Outside, Alan asks if she's all cut up about leaving Cass Carnaby and his band behind, but she says she is getting use to this "hello, goodbye" thing, and that it is always nice to get home again.