Mark, a software developer, had ordered the 100 micrograms of acid through a listing on the online marketplace Silk Road. He found a seller with lots of good feedback who seemed to know what they were talking about, added the acid to his digital shopping cart and hit "check out." He entered his address and paid the seller 50 Bitcoins—untraceable digital currency—worth around $150. Four days later the drugs, sent from Canada, arrived at his house.