Methamphetamine - "meth" - is considered one of the hardest addictions to quit. This dangerous drug craze is ravaging rural communities and spreading its poison to major metropolitan areas and across international borders at an alarming rate. What makes this drug so powerful, addictive and destructive? National Geographic correspondent Lisa Ling infiltrates the epidemic to uncover the madness of meth and expose the factors that make it the World's Most Dangerous Drug. She uses exclusive camera access and takes you into lab busts, police surveillance and many harrowing personal accounts through her investigation.