1944. Rosie Sinclair is proud to be doing her bit for the war effort as a driver at Cottisbourne Park - the secret heart of Britain's fight against Germany where a team of codebreakers are battling to save the country. But when she's given a mission to drive Major-General 'Bluff' Kingsley-Flynn down to Cottisbourne Rosie finds herself on the frontline of a new battle - to uncover a possible spy at the Park who is jeopardising their work and to resist her own attraction to the dashing Bluff himself. . . As the threat to her fellow codebreaker girls grows ever stronger Rosie realises her country needs her more than ever. Can she save the day without losing her heart?