San Francisco, Calif. — the epicenter of the 1960s' psychedelic revolution — is notorious for drugs. But in the new millennium, the city, especially the gay community, is struggling to recover from a meth epidemic. The enabler of this situation is the Asian cartel, which has been poisoning San Francisco with high quality meth for almost 25 years — but the Mexican cartels are intent on taking over. Nat Geo goes inside one of the worst drug ghettos in America — the heart of the drug trade.