Last episode we saw Klaus Fuchs steal details of the American atomic bomb for the Soviet Union. But he's only one component of a much bigger conspiracy. Today, Astrid introduces you to the mysterious web of Soviet atomic spies. Their work will change our world forever.

She's the gambler with a hotline to the Abwehr. The party girl tearing up the London social scene. Now she's doing her bit to hold back the Panzer Divisions and pave the way for D-Day. This is the story of Elvira Concepcion Josefina de la Fuente Chaudoir, Double Cross's most flamboyant double agent.