London 1939. In the weeks before the beginning of the Second World War, the Say When jazz club keeps London's Shoreditch swinging. Run by Thomas (Richie) and his wife Massie (Natasha Wightman), it's a place where gangsters and aristocrats, home office gents, and loose women can kick back and relax. Thomas' job is to keep everything running smoothly. But when he starts having an affair with singer Butterfly (Joely Richardson), this carefully balanced world disintegrates into blackmail, drugs, and suicide.

Major real-life air disasters are depicted in this series. Each episode features a detailed dramatized reconstruction of the incident based on cockpit voice recorders and air traffic control transcripts, as well as eyewitnesses recounts and interviews with aviation experts.