The British Foreign Office, led by Foreign Secretary Sir Edward Grey, receives news of an assassination in the Balkans. In Berlin, the Kaiser thinks he can exploit it to his own advantage.

War in Europe is becoming a real possibility. Under pressure from the Cabinet, the British foreign secretary unravels a tangled web of intrigue between Austria, Germany, Russia and France.

Sir Edward Grey seems unsure of whether to keep Britain out of the conflict. Desperate negotiations, resignations and a battle of wills in the Cabinet reach a crescendo with Germany's ultimatum to Belgium.