A former marine is trapped in an elite underground fight club. When cops swoop in they discover only one man left alive, him. But all is not as it seems. Is he the sole survivor or a mass murderer?

The story of Vera Atkins, a crafty spy recruiter, and two of the first women she selects for Churchill's "secret army": Virginia Hall, a daring American undaunted by a disability and Noor Inayat Khan, a pacifist. These civilian women form an unlikely sisterhood while entangled in dangerous missions to turn the tide of the war.