Plunge head-first into the gritty underworld of some of America's most fearsome prisons. In this world of absolutes, predators stalk their next prey, gang commanders order hits from isolation, and inmates are armed with deadly weapons.

But the prisons are striking back. Institutional weapons of choice include state of the art surveillance and old school isolation. Officers are armed to the hilt with steel batons and pepper spray. National Geographic Channel's cameras are there, in the middle of this real-life war zone, where only the strong—and the devious—survive.