A crooked investor called Warren Grafton tries to recruit Lady Penelope into aiding his scheme to build a cross-country monorail. When Penny informs Jeff, he investigates, but he, Brains, Warren and Tin-Tin find themselves trapped onboard a fully-automated monorail train speeding towards a stricken bridge.
Parker answers the door to reveal a man called Warren Grafton. He has an appointment with Lady Penelope Creighton-Ward. Unfortunately, Penelope is running late; she is being tailed by two gangsters. After failing to lose them via smoke and oil, she manages to get rid of them with the car's two rear machine guns. Whilst waiting for Penelope in one of the rooms, Grafton observes a transmitter hidden in the cigarette holder and Penelope's jewellery safe. He inserts a device behind the curtain to turn off the alarm.
When Penelope arrives home, she meets Grafton and their appointment commences. Parker recognises Grafton's cab driver, Harry Malloy, as a former gangster who used to work for the American Mob. Grafton informs Penelope that his company has built a monorail. It is not funded by the government, so Grafton is seeking sponsors. He is looking for an investment of $40million. Parker informs Penelope of the driver, so Penelope accepts. She does not have the $40million, but points out that a rich friend of her's may be interested.
The friend is Jeff Tracy, the founder of International Rescue. Penelope provides Jeff plenty of detail on Grafton's project. Jeff agrees to observe the monorail, considering their suspicions within the project when Scott Tracy points out they haven't had support from the US government in debating about safety precautions. Meanwhile Grafton meets his employees at his office in New York City, discussing how they'll get the money illegally. His plan is to talk Jeff into making the investment, while Malloy and Selsden rob Penelope's valuables.
The next day, Jeff, Brains and Tin-Tin join Grafton on the monorail. They are interested in how the monorail works. Grafton insists there's nothing wrong with the monorail. Elsewhere, Heli-jets are keeping an eye on the track. One of them gets struck by lightning during a thunderstorm. The pilot survives, but the helicopter crashes into the bridge, causing part of the track to collapse. The whole track, however is on the verge of collapsing. The brake pipe also snaps causing the automatic signals to be deactivated.
Jeff, Brains and Tin-Tin fear that Grafton may be a capitalist, who cares more about money than people's lives. Grafton picks up a signal and informs the rest that they're heading for the wreckage. Brains and Tin-Tin realise that the train cannot be stopped without an automatic signal. Jeff calls International Rescue, transmitting on a broad-range frequency and introducing himself as a stranger to convey the situation without Grafton realizing the truth. John, who receives the call, informs his brothers of the emergency, and Scott and Virgil set off with Thunderbirds 1 & 2 as quickly as possible.
Meanwhile Malloy and Selsden sneak into Penelope's mansion, assuming all of the alarms are switched off. But as they open the safe, a secret alarm in Penelope's side light sounds and is heard only by Penelope & Parker. The thieves are about to escape, but Penelope and Parker shoot the tires. The thieves come with a plan B, to use FAB 1 instead. However Penelope locks the doors and steering wheel via remote, trapping the thieves inside. The car spins continuously around the statue.
Back in the monorail, the situation does not improve. Brains attempts to stop the monorail one last time and manages to apply the brakes. The monorail brakes violently and stops just as it reaches the wrecked piece of track. But they appear to be dangling dangerously. Just in time, Scott arrives in Thunderbird 1, to inform Jeff, Brains, Tin-Tin and Grafton that they are still in danger. He instructs them to climb out of the train and onto the platform, but the platform collapses. International Rescue try a second attempt; Scott instructs the passengers to climb in the middle coach, while Virgil, who has arrived in Thunderbird 2, does the rest. He uses a set of magnetic grabs to lift the middle coach away. The rest of the monorail collapses and Thunderbird 2 lowers the coach down to safety. All the passengers have survived. Jeff, annoyed with Grafton's capitalist scheme, announces that Grafton will be spending the next part of his life in jail. Grafton is sceptical about it, but he and his other colleagues do end up in prison. His optimism that he'll become president of the monorail company fail to impress the other prisoners. The one thing they all have is time. Plenty of it.
Regular Voice CastEdit
- Jeff Tracy - Peter Dyneley
- Scott Tracy - Shane Rimmer
- Lady Penelope Creighton-Ward - Sylvia Anderson
- Virgil Tracy - David Holliday
- Alan Tracy - Matt Zimmerman
- Brains - David Graham
- Parker - David Graham
- Tin-Tin Kyrano - Christine Finn
- John Tracy - Ray Barrett
Guest Voice CastEdit
- Warren Grafton - David Graham
- Harry Malloy - David Graham
- Doolan - Matt Zimmerman
- Selsden - Ray Barrett
- Investor Hugo - Peter Dyneley
- 2nd Investor - Ray Barrett
- Helijet Pilot Joe (Patrol 304) - Ray Barrett
- Helijet Pilot Stan (Patrol 538) - Matt Zimmerman
- Crook with Machine Gun - Ray Barrett
- Helijet Patrol Base (not seen on screen, voice only) - Matt Zimmerman
International Rescue Equipment UsedEdit
Non-International Rescue Equipment UsedEdit
- The monorail train in this episode uses the same model as the one in The Perils Of Penelope. It was constructed by using pieces out of a Meccano bridge set.
- When Malloy and Selsden break into FAB 1 by smashing the glass, it is unknown how they managed to do it in such a short time. First of all, the transparent roof is a glass-steel canopy, and secondly, it would have taken a very long time to break the glass-steel canopy.
- Main article: Brink Of Disaster/Goofs
- Main article: Brink Of Disaster/Transcript
- French: Le monorail; Arrêtez le train
- German: Am Rande des Unglücks
- Spanish: Al Borde del Desastre
- Italian: Una truffa ben organizzata
- Dutch: De dodenrit (TV 1967); De laatste redding (TV 1991); Op het randje (VHS, DVD)
- Japanese: 恐怖のモノレール