And just beyond that, perched on the edge of a moss-covered lava field: the massive matte-white box that housed the Thor Data Center. That's why Tarbell and two US attorneys had come all this way. Thor was the home of a computer with a very important IP address, one that Tarbell and his FBI colleagues had discovered back in New York—the hidden server for a vast online criminal enterprise called Silk Road.

They'd been working on this case for months, as had federal agents across the country, in a wide-ranging digital manhunt for Dread Pirate Roberts: the mysterious proprietor of Silk Road, a clandestine online marketplace that functioned like an anonymous Amazon for criminal goods and services. Silk Road investigations had been launched by Homeland Security, the Secret Service, and the DEA office in Baltimore, where an agent named Carl Force had been working an undercover identity as a Silk Road smuggler for more than a year.