The presenter reaches the Middle Ages, exploring how the collapse of the Roman Empire had allowed the Vikings to lay the foundations of powerful new trading states as they pillaged their way from Europe to North America, while Muslim scholars in Baghdad's House of Wisdom built upon the knowledge of ancient civilisations from India, Persia and Greece. By exploring the conquests of Genghis Khan, the adventures of Marco Polo and the extraordinary story of the wealthiest African king who ever lived, Marr finds out how Europe used influences from around the world to rise again with the Renaissance. If Dragon's Den is more your bag, they're looking at the merits of toffee vodka.