A thick fog has blanketed much of Britain for 48 hours, halting all air and rail traffic. At London Airport, no flights are coming in or going out, but the British Overseas Airways Corporation (BOAC) and the other airlines are transporting people stranded at the airport by bus to other airports where flights are still operating.
Elderly and belligerent Miss Cynthia Beeston (Dame Margaret Rutherford), who believes the world should revolve around her and her alone, is able to commandeer one of the BOAC buses to take her and three other passengers – unaware ingénue Janie Grey (Belinda Lee), staid Edward Schroeder (George Coulouris), and milquetoast Henry Waterman (Toke Townley) – to Blackbush Airport.
A last-minute addition is suave Peter Jones (Terence Alexander), a pilot. Pretty and no-nonsense Lee Nicholls (singer Petula Clark), a flight attendant, serves as the attendant on the bus.
Unfortunately, their bumbling emergency relief bus driver, Percy Lamb (Frankie Howerd in his movie debut), has never driven to Blackbush and has enough problems working his way around London Airport in the fog!
The entourage is unaware that a £200,000 gold bullion robbery has just occurred and the robbery mastermind – nicknamed “The Banker” – has stashed the loot on their bus. The Banker is likely to be one of the seven of them, placing the lives of the other six in danger if The Banker is discovered and cornered.
The Police discover where the gold bars are – but the bus is lost somewhere in the fog.
In the last half-hour of the last day of shooting, director Val Guest realised he hadn’t enough material in the can to qualify the film as a feature-length production. Frankie Howerd told Guest to point the camera at him, went into a prop telephone box and – completely unrehearsed – ad-libbed a five-minute scene of him talking to his grandmother.
Miss Cynthia Beeston
Detective Inspector Henley
1st Transport Officer
2nd Transport Officer
3rd Transport Officer