National Geographic examines the gritty underworld of some of America's most fearsome prisons. With exclusive access and intimate interviews with inmates, this three-part program presents an unprecedented look at life in prison for a "prison pretty" newbie, vicious gang leaders and a gangster turned rat. Viewers will explore a world where gang commanders order hits from isolation, inmates are armed with deadly weapons and only the strong -- and devious -- survive. Episodes: Lockdown: Gangland, Lockdown: Predators Behind Bars, Lockdown: Inside Maximum Security