America's Deadliest Gang: MS-13.

It's the most violent gang in America. It has 10,000 foot soldiers in the US, spreading its brutal ways across 33 states. And now, it's going global, fueled by migration across the Western hemisphere and leaving its bloody mark from Central America to the American heartland. Police in half a dozen countries struggle to crack its code and decipher its methods. Now, for the first time, we get answers from the inside.