Richard Hannay meets Sybil Verney, a beautiful woman who is also of South African origin. Unlike Hannay, who feels 'surrounded' in London and prefers the wide-open spaces of Africa, Sybil is very fond of England and of its society.

Very quickly, Richard Hannay falls under her spell; he falls desperately in love for the first time in his life, but Sybil Verney has a secret. She is being blackmailed by Sir Marcus Leonard, a ruthless gambler and racehorse owner, who has a hold over Sybil. The secret is to be found in some letters which Sir Marcus has securely locked away in his safe.

Richard Hannay offers to get the letters for Sybil, but in order to do so must take some lessons in safe-breaking from Sal Alford. He is an apt pupil, managing to break into Sir Marcus's safe, while Sal acts as guard outside. Unfortunately, he is caught by Sir Marcus, but Sal escapes with the incriminating letters.

Sir Marcus convinces Hannay that Sybil is a liar and a cheat. Who is telling the truth?