Cambridge University in 1937 is awash with ideas and idealists - to unworldly Joan it is dazzling. After a chance meeting with Russian-born Sonya and Leo, Joan is swept up in the glamour and energy of the duo, and finds herself growing closer and closer to them both. But allegiance is a slippery thing.

‘If you loved William Boyd’s Restless, you’ll enjoy this’ Viv Groskop, Red

Cambridge University in 1937 is awash with ideas and idealists – to unworldly Joan it is dazzling.

After a chance meeting with Russian-born Sonya and Leo, Joan is swept up in the glamour and energy of the duo, and finds herself growing closer and closer to them both.

But allegiance is a slippery thing. Out of university and working in a government ministry with access to top-secret information, Joan finds her loyalty tested as she is faced with the most difficult question of all: what price would you pay to remain true to yourself?

'A gripping, emotional and expertly plotted spy novel of the Cold War, inspired by a real story. Beautifully written and clever' Kate Mosse

NOW A MAJOR FILM STARRING JUDI DENCH AND SOPHIE COOKSON