Athens in 490 BC is a small, fragile democracy facing invasion by the Persian empire of Darius the Great. This episode follows the general Themistocles as he pushes the city from that first crisis through decades of war and rebuilding. The courier Phidippides runs to Sparta to beg for help before the Battle of Marathon, and when Sparta refuses, Athens fights alone and wins. Themistocles reads the victory as a reprieve, not an ending, and convinces Athens to build a fleet of ramming warships called triremes. When Xerxes succeeds his father and marches on Greece with a vast army, the Delphic Oracle's cryptic promise of a "wooden wall" becomes the pretext for evacuating Athens and staging a naval ambush at Salamis, where the triremes sink roughly two hundred Persian ships. Liam Neeson narrates, with computer reconstructions rebuilding the Acropolis and restoring the Academy. The episode closes with Pericles overseeing the Parthenon's construction and the intellectual flowering that follows the war.