During the spring and summer of 1918, with World War I still undecided, British, French and American agents in Russia developed a breathtakingly audacious plan. Led by Robert Hamilton Bruce Lockhart, a dashing, cynical, urbane 30-year-old Scot, they conspired to overthrow Lenin's newly established Bolshevik regime, and to install one that would continue the war against Germany on the Eastern Front. Lockhart's confidante and chief support, with whom he engaged in a passionate love affair, was the mysterious, alluring Moura von Benkendorff, wife of a former aide-de-camp to the Tsar.

The plotters' chief opponent was 'Iron Felix' Dzerzhinsky. He led the Cheka, 'Sword and Shield' of the Russian Revolution and forerunner of the KGB. Dzerzhinsky loved humanity - in the abstract. He believed socialism represented humanity's best hope. To preserve and protect it he would unleash unbounded terror.

Revolutionary Russia provided the setting for the ensuing contest. In the back streets of Petrograd and Moscow, in rough gypsy cabarets, in glittering nightclubs, in cells beneath the Cheka's Lubianka prison, the protagonists engaged in a deadly game of wits for the highest possible stakes - not merely life and death, but the outcome of a world war and the nature of Russia's post-war regime.

Confident of success, the conspirators set the date for an uprising, September 8, 1918, but the Cheka had penetrated their organization and pounced just beforehand. The Lockhart Plot could have been a turning point in world history. Instead, its failure has left us with one of the great 'what ifs?' of twentieth century history, which is why it has until now remained shrouded in mystery. But it was a plot on whose outcome rested both the fate of the Revolution and the future shape of world history - and the story behind it is a thrilling one that continues to resonate in the early 21st century.