A series of inexplicable accidents befall the development of the world's first supersonic airliner, the SST1 – a man falls victim to a homicidal air stewardess (an uncredited Maria Aitken) and two women (Yutte Stensgaard and an uncredited Joanna Lumley) perform separate acts of sabotage during tests. The Air Ministry calls on Hugh "Bulldog" Drummond (Richard Johnson (actor)) to investigate.