Penelope and Parker are at a casino. Parker is losing, so Penelope tells him it doesn't seem to be his night. She decides to take over and places a bet. She says that, after all, it is her money. She bets on twelve red. As the roulette wheel spins, Penelope hears another woman at another table.

The woman has just lost, having wanted her wheel to land on seventeen black. She says that makes 750,000 she's lost, but thinks she'll make it up this time. Penelope says that's the Duchess of Royston, someone she hasn't seen for years. She tells Parker to sit in for her, whilst she heads over to the Duchess' table. The Duchess has bet again on seventeen black.

But the crooked croupier discreetly uses a control panel on the table, which lets him pick where the wheel will stop. It stops on eighteen red, which means the Duchess has lost again. Across the table, two men have been watching. Chandler tells his buddy Brophy that this lady is so stupid she can't even tell that the table's been fixed.

The Duchess then places down her headpiece and uses that to bet with. She then sees Penelope and says this is a delightful surprise, but she fears she's doing rather badly at gambling. Penelope says that looks like a desperate measure, but the Duchess says she's a desperate woman, as all she's got left now is her painting -her precious Braquasso. She's glad she left that at home, otherwise she'd be gambling that away too. The wheel then starts spinning again, but it stops at fourteen red, meaning the Duchess has lost again. She says she really has lost everything.

Penelope gets up and says this table is fixed! The croupier says she's mistaken, but he activates a silent alarm. This lets the casino's owner know something is up, so he cuts the power to the casino. The lights all suddenly go out.

He starts stuffing money from a safe into a bag, but Parker comes in and tells him not so fast. The owner grabs a gun and starts firing, and gets into a shootout with Parker. Parker tells him the game is up, they've got witnesses to prove it.

The owner asks what he's talking about, and Parker says the tables are fixed. The owner asks if they can come to an understanding, but as Parker asks him what he wants whilst hiding behind cover, the owner uses a secret door to escape. Penelope comes in and Parker tells her the owner got away, and took his money with him. Penelope says she lost the Duchess when they threw the lights downstairs, but says they'd best go after the owner.

The owner gets to a car outside, which the croupier is driving. As they speed away, they are seen by Penelope and Parker, who quickly get to FAB 1 and go after them. Penelope tells Parker he'd better prepare, just in case. Parker has FAB 1's cannon switched on.

The owner starts firing at them with a machinegun. Penelope tells Parker to try and get the tires first, they may as well attempt to reason with them. FAB 1's gun starts firing, but Parker is unable to hit the car. He says it's no good, there are too many bends in the road.

The casino owner's car heads down another road, which Parker misses. It gets to a building and hides in the garage, where the door closes. Parker says they've lost them, but Penelope says never mind. She tells Parker they'll go and console the Duchess, who she believes is staying at The Grand. Penelope goes to the hotel, but is told that the Duchess has already checked out. The receptionist says the Duchess can be found at Royston Castle in England.

The castle is for sale. Penelope and Parker arrive there, but Parker thinks they are too late. Penelope says that it seems Deborah wasn't joking when she said she'd lost everything. She wishes there was something they could do to help her, and she's glad Jeff's coming over for the air display. Perhaps he can think of something, as rescues are his forte. At Tracy Island, Grandma asks Tin-Tin where Jeff is. Tin-Tin says the last time she saw him, he was carrying that big parcel that came to him in the post today.

Jeff is practicing his best British accent whilst wearing his new suit. He's soon at London Airport, where the air display is taking place. He meets with Penelope and he says this is what he's been wanting to see -the new carrier craft. He and Penelope take out their binoculars.

They watch as a small jet lands on top of the carrier craft. The pilot of the jet ejects, as Jeff says that the other machine will guide both craft down. The carrier jet lands on a runway successfully, still carrying the smaller jet.

Two Air Force guys are watching. Percy thinks this is all first class, and his friend thinks this is all very well, but International Rescue are doing this sort of thing all the time -they ought to have them on display! Jeff and Penelope quickly turn away.

Later on, Jeff and Penelope attend an art museum. Penelope asks him if he must fly off to New York tomorrow, and he says he's afraid so. Penelope says this is an exhibition of art of the last century. She tells Jeff about the Duchess of Royston, who has fallen on hard times. She went to the south of France to try and corner the market there, but the stakes were rather against her. Jeff asks if there is anything they can do. Penelope says the Duchess has had to lend her last previous possession to the gallery to try and recoup a few of her losses. She shows Jeff the painting, "Portrait of a Gazelle" by Braquasso. Jeff looks at it and says he thinks he knows how they can the Duchess out of her difficulties. There's someone in New York he's got to go and see.

Jeff arrives at the Gazelle Automation Inc building, and enters an elevator. The computer inside it speaks, welcoming him and asking him who he's here to see. Jeff explains he has an appointment with Mr Wilbur Dandridge the Third. The computer voice tells him to take a seat, and a seat appears out of one of the walls.

Jeff arrives in Wilbur's office. Wilbur says he hasn't seen him in years. Jeff tells him it's some elevator he's got, but Wilbur tells him he hasn't seen anything yet. At Gazelle Enterprises they've got everything automated. He asks Jeff if he wants a cigarette, and part of the table opens up revealing several pre-lit cigarettes and cigars.

Wilbur asks him what he wants to drink. Jeff says he'll have a whiskey on the rocks. Wilbur says no problem, as another machine opens up in a cabinet and pours the correct drink. Wilbur asks if the sun is too bright, and activates the blind. But it stops half way before suddenly dropping down. Wilbur says he must get that fixed sometime, but then asks about this "Portrait of a Gazelle". Jeff says he knows of Wilbur's fondness for gazelles, so he thought he'd be interested. He shows him a reproduction of the painting.

Wilbur looks at the reproduction and says it's sensational, he's just got to have this picture. He thinks it could be the symbol of the whole Gazelle organization! Jeff says that's what he'd figured, but warns that the Duchess may not want to sell. Wilbur says she'll sell alright.

He flies to Penelope's home in England and gets to see the real picture. He calls it a perfect gem and says whilst he doesn't know much about art, he does know what he likes. This painting is sensational, and he asks Penelope if she agrees. Penelope says it's a good example of Braquasso's middle period and it's an honor to have it inside her home. The Duchess thinks it's so sweet of her to look after it for her now the exhibition is over. As Penelope summons Parker, Wilbur makes the Duchess an offer for the painting: 475,000. The Duchess says she's afraid the picture isn't on the market.

Wilbur says she can't frighten him off, he knows a good investment when he sees one. He's set his heart on that painting, and he aims to have it. The Duchess says she does hope she's not casting aspersions on his business ability, but the offer he has made seems so disproportionate.

Wilbur says she drives a hard bargain, but he's willing to advance his figure. He then offers her 600,000 pounds for the painting. The Duchess says no thanks, as that picture is a precious family heirloom and she couldn't near to part with it. Wilbur says he came all the way from the United States for that painting. Penelope says they should drink their tea and try to find a good old British compromise -a solution to make both of them happy. She suggests the Duchess could let Wilbur have the painting for six months on a rent basis. Wilbur thinks that's a great idea.

At London Airport, a Fireflash is being prepped for takeoff to New York. In the lobby, the Duchess hears anyone going on the Fireflash needs to join their hostess in two minutes on moving walkway number three. The Duchess wonders if three is a lucky number or not. Penelope says she has a going away present for her that'll give her luck. She passes the Duchess a box and says there is a St Christopher inside it.

Penelope tells her if she wears it, she'll have a safe journey. Parker has seen to the loading of the painting, so she should have nothing to worry about. Wilbur's chauffeur will be meeting her at the other end. The Duchess thanks her for bearing with her, as she must appear sometimes like an eccentric old woman, but that painting really is precious to her. She'd feel happier if she took it over to Mr. Dandridge in person. A hostess then comes over and tells the Duchess they're ready for her now. The Duchess says goodbye to Penelope. Penelope tells her not to forget to wear the broach. The Duchess says she won't, and says she mustn't forget her umbrella either.

A little later on, the Fireflash takes off and leaves London Airport. The Duchess thinks it was so nice of Penelope to give her this, and opens the box. She thinks the broach is pretty, and puts it on.

The broach has a tracker inside it, which is being monitored by Penelope. She says it'll be nice just to keep a check on the Duchess' progress with this. In New York, Wilbur tells Hendrix he'd better go to the airport as the Duchess' aircraft should be coming in soon. He makes sure Hendrix has got the cheque, and Hendrix says he has it right here. Wilbur says the cheque will show her they mean business just in case she's changing her mind.

As the call ends, someone hits Hendrix on the back of the head. Chandler and Brophy have arrived and says it's going to be a cinch to get the Duchess. Meanwhile, the Fireflash lands in the New York Central Airport.

The Duchess collects her luggage, which includes the painting. Brophy goes up to her, now wearing Hendrix's uniform. The Duchess says he must be Mr. Dandridge's chauffeur. He asks if he can carry her bags, and then asks if that's the painting. She says yes, but says there was a certain arrangement. Brophy says she means this, and shows her the cheque.

Penelope and Parker have returned home, and are watching where the Duchess is from there. They see she's reached New York, but Parker says she's already moving away from the city. Penelope says she hopes everything is going according to plan. Meanwhile, Brophy takes the Duchess away in a car. She asks if this is Central Park, but he says it isn't, and they aren't going to New York City. She asks why, and he says Mr. Dandridge asked for her to be taken to his country house.

Penelope says she doesn't like this, as the arrangement was for Mr. Dandridge to take the Duchess to his New York office to watch the hanging of the painting. Brophy's car comes to a stop at a house, and the Duchess asks if this is Mr. Dandridge's country house. Brophy claims that it is. Penelope contacts Wilbur, and he says he was about to contact her. She asks what has happened to the Duchess, but Wilbur says he doesn't know. His chauffeur was to bring her here, but they're terribly overdue.

Penelope says the Duchess must have been kidnapped. The video feed is then cut off, so Penelope contacts Jeff. She says that the Duchess' signal has led deep into the country. She's clearly been intercepted as someone posing as Mr. Dandridge's chauffeur. Jeff says they'll find her, and tells Scott to go. He'll get John to track the exact course of the Duchess' bleep signal, then have him contact Scott once he's airborne.

As Scott leaves, Jeff tells Virgil he'd better take off in Thunderbird 2, as there's no knowing what may be in store for the Duchess. Penelope then says that the Duchess' signal has stopped moving, but Jeff thinks that'll make it easier for John to get a precise fix on it. Thunderbird 1 then takes off.

Thunderbird 2 also takes off. In Thunderbird 5, John reports to Thunderbirds 1 and 2, giving Scott and Virgil the coordinates to where the Duchess is. He says it's a lonely spot. At the house, Brophy has taken the Duchess to the basement and tied her up. She asks him what it is he wants, and if it's the painting, he can take it.

Brophy says they've taken it, he managed to slip it to his buddy at the airport whilst she was changing her currency. The Duchess says he'll never get away with this, but Brophy says they will, just like those crooks at the casino got away with her dough. The Duchess realizes she did see Brophy at the casino before. But she then says she can smell gas. Brophy tells her he wouldn't go around striking matches if he was her, otherwise there could be a nasty explosion. He then leaves, leaving the Duchess thinking what's to become of her.

Scott asks what the latest from the Duchess is. John tells him it's still the same, the transmitter is still signaling from the same location. Scott says they can only hope she's still wearing the broach, and the signal isn't leading into a trap. At the house, the Duchess says that gas is leaking all over the place. She decides she's got to get out of here somehow, and starts rocking on the chair. As she does, she ends up hitting a ladder.

The ladder falls and hits something that causes a small explosion. Thunderbird 1 hovers outside the house and reports it's a pretty solitary spot. But the house then explodes. John says that the Duchess is still transmitting, so Scott says he'll go into land now.

Wilbur is told that the Duchess of Royston's representative is here to see him, and has the "Portrait of a Gazelle" with him. Wilbur contacts his secretary and tells her to get the police over here right away, as he thinks they've caught the guy who took the painting. He then activates the blind, which stops halfway down. Chandler then arrives via the elevator, and says he's here to deliver the painting to him and collect the second installment of the payment in cash.

Wilbur asks his secretary to send in the cash payment for the painting. She says she will, and also mentions that the other matter is now in hand. Chandler asks what the other matter is, but Wilbur asks to see the painting. Chandler reveals it, and Wilbur says it's the real thing alright. The money is then sent into the room, but when Wilbur opens the box, it has a gun inside it. He grabs it and tells Chandler to put his hands up.

The blind then suddenly drops down, and during the distraction, Chandler throws the painting at Wilbur. Wilbur fires just as it hits him, and is distraught to see that the bullet has hit the painting and ruined it!

Scott tells Virgil that he's traced the Duchess to the cellar, as there's a very definite signal coming from underground. The house continues to explode and collapse, with the main structure mostly destroyed already. Virgil then arrives and lands Thunderbird 2 near the house.

Scott says they'll need the Mole, as they need to get into the cellar quick. Virgil brings the Mole out of pod 3, and heads towards the house. Scott gives him the the course coordinates. Scott says he'll go and get the restraining outfit, as when that wall goes over, the basement will never stand the weight.

In the basement, the Duchess has survived, but says she'll never get out alive. A piece of debris then hits her on the back of the head, causing her to collapse. Outside, Virgil arrives at the coordinates Scott gave him, and has the Mole start drilling into the ground.

Scott goes into pod 3 and mans the Domo. He asks Virgil how it's going, and he says no snags so far. Scott then drives the Domo out of the pod, and heads towards the house. He has the Domo's three suction clamps attach to the wall, and starts to drive backwards. But the wall is still about to go over.

The Duchess gets up. Scott tells Virgil to hurry it up, as the wall is going to give away at any moment. Virgil says this soil seems to be in a vein of solid rock. Scott says this heat is fantastic, as the flames get around the Domo's suction clamps.

The Mole drills into the house's basement, leading the Duchess to question what it is. Virgil appears and tells her to come quickly this way, so the Duchess gets up. But before she leaves, she's sure to pick up her umbrella.

Scott says he can't sustain the wall any longer. Virgil says they're on their way up now, but the suction clamps fall away from the wall. The wall topples over and hits the remains of the house, causing the basement to collapse. Scott reports to base that Virgil was on his way up with the Duchess in the Mole, but the whole building has gone over. He can't get any reply, so either the radio is smashed or he's in a bad way down there. Jeff asks if the Duchess' signal is still registering. Scott says that it is, but he can't tell if it's moving or not.

Jeff tells him to keep standing by. He tells Alan and Tin-Tin that if only they could have known in advance about the rescue conditions. Alan says they could have taken the pod with all the fire-fighting gear. Tin-Tin tells them not to blame themselves, as if they'd waited to find out what had actually happened to the Duchess, it would have been too late to attempt a rescue anyway. Scott then see the Mole reach the surface again. The Duchess is taken to a hospital, where Penelope visits her. The Duchess says the property development company backed out when the project was dropped, and the agent couldn't sell her home. Penelope thought the Duchess was relying on that sale.

The Duchess says it was ideal, as she was able to buy back her home. Penelope says she doesn't understand, but the Duchess explains it was paid for with Mr. Dandridge's cheque. Penelope says she has sad news about the painting, but the Duchess says she doesn't want to be depressed. She's just been rescued by those romantic young men from International Rescue, and the FBI have got the man who impersonated Mr. Dandridge's chauffeur. Interpol have arrested the men who were running that crooked casino, and she's going to get back all the money she's lost. Wilbur then walks in and whilst he's glad to see she's well, the truth is he has some rather sad news about the Gazelle picture. He says the picture has been destroyed, and it was his fault. The Duchess asks if he's positive, and he says he is.

The Duchess reveals her umbrella and pulls out something from it. She asks Penelope to open it, as the Duchess says she has some news for Mr. Dandridge. Penelope opens up the painting, which the Duchess says is the real one. The one Wilbur had was a copy, so she asks if he could kindly oblige her with the second half of the loan payment, the picture will be his for the next six months as agreed.

Parker walks in and says there's a glossy magazine on the videophone for the Duchess. They want the rights to her life story, and are willing to pay her 35,000 pounds. The Duchess says she'll take 50,000 pounds -nothing less. She then asks Parker about the 3.30 race. Parker says bad news, the 3.30 was won by Desperate Intruder, a rank outsider. The Duchess says that's a pity, although she knows her luck is changing. Once she's up and about again, there's a little trip she wants to take.

At another casino, the Duchess has resumed gambling, this time betting on fifteen black...