American entrepreneur Warren Grafton arrives at Creighton-Ward Mansion to approach
Lady Penelope as a potential investment partner in his new venture: the fully-automated Pacific Atlantic
suspended monorail. The meeting is delayed while Penelope, driving home in
FAB 1, deals with two criminals who are tailing her – first deploying her car's
smoke screen and oil slick, then using its machine guns to blast the villains'
convertible off the road. Grafton exploits Penelope's absence to locate her jewellery safe and conceal a
burglar alarm-jamming device in the mansion.
Parker recognises Grafton's chauffeur as Harry Malloy, an ex-mobster. On meeting Grafton, Penelope declines to invest in the monorail and refers Grafton to her industrialist friend and secret employer,
Jeff Tracy. Although Grafton has clashed with the
United States government over inadequate
safety measures, Jeff agrees to ride the monorail before making up his mind about the project, joined by
Brains and
Tin-Tin as technical advisors. Unknown to Penelope and Jeff, Grafton is the head of a
crime syndicate. Meeting his associates, Grafton outlines his plan to fill a gap in the monorail's funding: Malloy and fellow syndicate member Selsden will break into Penelope's mansion and steal her multi-million-pound jewellery collection. The next day, Grafton and his guests set off in the monotrain. Jeff is unimpressed by his host's penny-pinching attitude to safety, especially on hearing that without train staff, the passengers' only nonautomated lifeline is a fleet of patrolling helijets. Jeff's concerns prove well founded when one of the helijets is struck by lightning, forcing its pilot to eject before it crashes into a bridge. The explosion destroys a section of track and knocks out the monorail's automatic
signals. No manual override exists to stop the train, so Brains and Tin-Tin devise a brake switch by modifying the
power unit. Meanwhile, Jeff radios International Rescue for help, taking care not to address his sons by name to maintain secrecy.
Scott and
Virgil take off in
Thunderbirds 1 and 2. The switch works and the train grinds to a halt on the bridge, just feet from the break in the line. The
Thunderbirds arrive. As the bridge buckles under the weight of the train, Scott directs the occupants to the middle carriage, which Virgil airlifts away using
Thunderbird 2s grabs. The bridge collapses, taking the train with it. Jeff warns Grafton that he faces a lengthy jail term for his negligence. In England, Malloy and Selsden wait until the middle of the night and launch their raid on the mansion, gaining entry undetected thanks to Grafton's jammer. However, they are unaware that the jewellery safe has its own alarm and inadvertently wake Penelope and Parker. Armed with a machine gun, Parker moves to a window and shoots out the tyres on the criminals' car to stop them getting away. Malloy and Selsden try to escape in FAB 1 but Penelope activates a remote control which locks the steering wheel, leaving them driving in circles. Malloy and Selsden are arrested and imprisoned with Grafton and the rest of the syndicate. ==Regular voice cast==