Could you spy on the woman you loved?

It’s 1938 and Europe teeters on the edge of war. In Berlin, life for Mila Nessian – genius mathematician, billionaire and womaniser – is one long party. A spot of rocket science by day, the Third Reich’s prettiest daughters by night. She knows what they whisper behind their hands – that Germany’s most dazzling mind has nothing but a calculator where her heart should be, a sliver of ice instead of soul. She smirks through yet another boring cocktail party and hopes they’re wrong.

Cecelia Balfour is dragged to Berlin by her socialite mother – and it’s the last place she wants to be. Cecelia has lost a lover and worries that her heart is too bruised to ever properly love again. To distract her, to maybe get her back in the game, her cousin at MI6 sets up a play: flirt with Mila Nessian, capture her secrets, lure her back to London.

Because what Mila is working on could steer the course of the coming war. The Nazis want her brilliance, British Secret Intelligence wants her silence, and Cecelia – once she has laughed with her, slept with her, sipped champagne on a Zeppelin with her and lost her heart to her – Cecelia wants her love.

Can she win Mila’s trust and save her from the powers that control both their lives?