FRONTLINE returns to Iraq, this time to embed with Halliburton/KBR, and to take a hard look at private contractors like Blackwater, Aegis and Erinys, who play an increasingly critical role in running U.S. military supply lines, providing armed protection, and operating U.S. military bases. These private warriors are targeted by insurgents and in turn have been criticized for their rough treatment of Iraqi civilians. Their dramatic story illuminates the Pentagon's new reliance on corporate outsourcing and raises tough questions about where they fit in the chain of command and the price we are paying for their role in the war.