Who Killed Athenian Democracy, Episode 4

For 20 years, Athens and Sparta fought, each unable to land a killing blow. But as the democratically elected Athenian leaders focused on the Spartans outside their walls, they lost track of the enemies within their own city. Treason brewed as oligarchs dreamed of murder.

Sources: 

• The Peloponnesian War, by Donald Kagan
• Lords of the Sea, by John R. Hale