The story opens with the discovery of a castaway by an Italian sea captain. Recovering in hospital in Trabazon, Turkey, the man is visited by an Anglo-Ukrainian Bank Clerk, Andrew Drake. The castaway, Miroslav Kaminsky, is a Ukrainian nationalist who escaped from Lvov after he was betrayed to the KGB. Drake, born Andryi Drach, convinces Kaminsky that they both share the same ideal, that of striking a single blow against the Soviet Union. Kaminsky tells Drake about Lev Mishkin and David Lazareff, two Jewish Ukrainian nationalists who may be able to help him.
Meanwhile, a chain of failures at the sole plant that makes fungicide for wheat has led to the inadvertent poisoning of the Soviet Union's wheat crop. The United States is aware of this crisis and plans to sell its food to the Soviets in exchange for political and military concessions. Hardliners in the Politburo come up with a different strategy: to take the food from the West by invading Western Europe. The Politburo, led by Chairman Maxim Rudin, narrowly votes down the war plan; however, Rudin is dying of cancer and it is only a matter of time before the party in favor of war gains time.
The news of the war plan comes to MI6 agent Adam Munro through a Russian woman he once loved, who works in the Kremlin offices and has access to the Politburo debates. This source, given the code name Nightingale, shakes both the British and U.S. political leadership. Munro is forced to call on Nightingale more and more, risking the near certain discovery and execution of the woman he loves.