Lethal Doses

On a cold afternoon in February 1991, a frightening new drug hit the streets of New York City, a synthetic narcotic marketed in packets labeled "Tango & Cash." As police scrambled to warn heroin users of the danger, the overdose victims began piling up in hospital emergency rooms and county morgues across three states.

As a Drug Enforcement Administration agent said at the time, "We don't know yet who's putting this stuff out there, but whoever he is, he's an ice-cold son of a bitch." Fent...