"Its use was not as widespread as MDMA, but it certainly caused a ripple in the drug market," says Andrew Camilleri, a forensic scientist at the South Australia Department of Justice. At the same time, it arrived in force in London and quickly took root in the underground club scene thanks to another marketing coup. Because it was being sold online as plant food, it had a certain curio value and cachet (in the "I'll try anything" drug ethos). The mephedrone high is shorter than that of Ecstasy, says Camilleri, who cowrote one of the only studies of the drug. "Some users report a terrible comedown; others say it is far better than the comedown of MDMA."

In fact, mephedrone packs two different highs, uniting two traditionally divergent drug crowds. It appeals to Ecstasy users because of its euphoric effects and to cokeheads because of its rush, which is less edgy, and thus more pleasant, than blow's. On top of that, coke is often cut with harmful chemicals. The DEA estimates that one third of all U.S. cocaine is tainted with levamisole—a veterinary deworming medicine. Because you buy mephedrone directly from an online supplier and not, say, a street dealer, it generally arrives 100 percent pure. All of which makes mephedrone seem like a narcotic holy grail—an unadulterated drug for all the people all the time. Of course, sometimes a drug can be too pure.

• • •

IN March 2009, a 16-year-old girl from Bend, Oregon, snorted a couple of lines of sunshine at a party. A 19-year-old guy had allegedly given it to her, telling her it was a pure form of Ecstasy. The next morning the girl's foster mother found her "having cold sweats, hyperventilating, shaking," according to a police report. At the hospital the girl vomited repeatedly and drifted toward unconsciousness. The effects lasted for days. The state crime lab was baffled when it finally tested a sample of the powder.

"I sent my data to labs all over the state and no one knew what it was," says Angela Mayfield, a forensic scientist at the Oregon State Police Crime Lab in Bend. She eventually sent the sample to authorities in Australia and learned what she had on her hands. "It was kind of shocking to find it here," Mayfield says. "But these MDMA analogs are going around now."

Drugs can jump borders and oceans like viruses, thanks to dealers and jet-set partyers and, of course, the Internet. While numerous websites tout mephedrone's high, so far it has come into public view in the U.S. only sporadically. In Bismarck, North Dakota, a head shop called Big Willies was selling it as a bath salt called star dust. In February, after two people who bought star dust overdosed and ended up in the hospital, the state moved quickly to ban mephedrone—it's the only one to have done so.

At the federal level, mephedrone enjoys a quasi-legal status. Technically, users can be charged with possessing or selling it under the 1986 Analog Act. But even the DEA says such cases would be difficult to prosecute, because authorities must prove that the drug is intended for human consumption. Therein lies the genius of marketing mephedrone as plant food—it's a de facto immunity amulet from felony prosecution. The 19-year-old in Bend who allegedly dealt the drug to his friends was charged with only a minor offense, delivering an imitation controlled substance. Rusty Payne, a spokesman for the DEA, says, "It would have to be a huge case for a U.S. Attorneys Office to want to pursue, because of the difficulty."

So why aren't more people doing it? Perhaps because outside the Burning Man crowd and the gay dance-club scene, Ecstasy isn't that big in America. Mephedrone will have to make inroads with the methed-up, Breaking Bad masses or the coked-up, dick-swinging Hollywood-Wall Street set to become a DEA priority.

"The funny thing is, you'll get faced doing a single 100-milligram line of this stuff," says Hamilton Morris, the host of Hamilton's Pharmacopeia on the online VBS.tv site and a self-styled modern-day De Quincey, who has tried mephedrone and enjoyed it. "It's pure—nobody is fucking with it. When you compare it to cocaine, which is horrifically contaminated, or MDMA, which is as dirty as it gets, it has a lot going for it. Convenience. Price. Purity. I'm not surprised it's huge in the U.K."