Twenty years have passed since Jean-Baptiste Poncet's daring mission to the remote and exotic court of the King of Abyssinia. We find him now in Isfahan, capital of Persia, practicing medicine in the court of the Shah. In order to rescue his old friend Juremi, imprisoned in the Urals, Poncet travels in disguise to Russia, where he engages in a diplomatic duel of wits with Peter the Great. The friends, reunited, are captured by nomads and sold as slaves in Afghanistan. This is the beginning of Poncet's circuitous return to Isfahan, where his wife and daughter are trapped by a besieging army of the Afghan king, Mahmud.