Half a million people live in Egypt's Sinai Peninsula, bordering Israel and the Gaza Strip. For decades, they have been governed by a strong security paradigm, and the Camp David accords with Israel - underwritten by billions of dollars in US military aid.
Now they are back in the international spotlight because of an increase in militant attacks, arms smuggling and human trafficking.
When Egyptians took to the streets against Hosni Mubarak's police state in January 2011, the Sinai was no exception. But the insurgency here continued long after his ouster, causing worry among some of Egypt's powerful backers.
The true test of the evolving Egyptian relationship with the US then may lie in Cairo's ability to control any instability in the peninsula.
Fault Lines explores the roots of Sinai's ongoing uprising and, as Egypt's new leaders vow to crack down on militancy and smuggling, the dangers of following an old script. How did the Sinai Peninsula become a crucible for geopolitical tensions?
Warning: Contains scenes which some viewers may find disturbing.