Renowned scientist John Sinclair and his old school friend Richard, a celebrated composer, are enjoying a climbing expedition in the Scottish Highlands when Sinclair disappears without a trace for thirteen hours. When he resurfaces with no explanation for his disappearance, he has undergone an uncanny alteration: a birthmark on his back has vanished. But stranger events are yet to come: things are normal enough in Britain, but in France it's 1917 and World War I is raging, Greece is in the Golden Age of Pericles, America seems to have reverted to the 18th century, and Russia and China are...