Berlin, 1943. A group of high-society anti-Nazi dissenters meet for a tea party one late summer afternoon. They do not know that, sitting around the table, is someone poised to betray them all to the Gestapo - revealing their secret to the Nazis' most ruthless detective.

They form a circle of unlikely rebels, drawn from the German elite: two countesses, a diplomat, an intelligence officer, an ambassador's widow and a pioneering headmistress. Meeting in the shadows, rescuing Jews or plotting for a future Germany freed from the Führer's rule, what unites them is a shared loathing of the Nazis, a refusal to bow to Hitler and the courage to perform perilous acts of resistance. Or so they believe.

How did a group of brave, principled rebels, who had successfully defied Adolf Hitler for more than a decade, come to fall into such a lethal trap? And who betrayed them?