Set in blacked-out London during the ominous lull before the Blitz, this true story centres on Tyler Kent, a debonair encryption specialist at the US Embassy - who also happens to be a Soviet mole. He becomes romantically entangled with Anna Wolkoff, a Russian fashion designer and Nazi spy. Together they steal the coded telegrams between President Roosevelt and Winston Churchill: if revealed, these messages would change the outcome of the war. Hot on the trail of Kent and Wolkoff comes the brilliant but eccentric British spymaster Maxwell Knight. He infiltrates the glamorous circle of fascist conspirators gathering in the Russian Tea Rooms, just a stone's throw from South Kensington tube station.