"You'll never get me up in one of those things. They're absolutely lethal."

Seville, 1931. Six months after the loss of the British airship the R101, a German Zeppelin is coming in to land in Southern Spain.

Hilary Manningham-Butler is an MI5 operative eking out a pitiful existence on the Rock of Gibraltar. The offer of a job in the Americas provides a potential lifeline but there are strings attached. First she must prove her mettle to her masters in London and that means stepping on board the Richthofen before the airship leaves Seville.

A cache of secret documents has been stolen from Scotland Yard and the files must be recovered if British security is not to be severely compromised. Hilary must put her life on the line to discover the identity of the thief. But as the airship makes its way across the Atlantic towards Brazil it becomes clear that nobody on board is quite what they seem. And there is no guarantee that any of them will reach Rio de Janeiro alive...