Before dawn on January 23, 2019, Mark McConnell arrived at the Key West headquarters of the military and civilian task force that monitors drugs headed to the United States from the Southern Hemisphere. McConnell, a prosecutor at the Department of Justice and a former marine, left his phone in a box designed to block electronic transmissions, and passed through a metal detector and a key-card-protected air lock to enter the building. On the second floor, he punched in the code for his office door, then locked it behind him. On a computer approved for the handling of classified information, he loaded a series of screenshots he had taken, showing entries in a database called Helios, which federal law enforcement uses to track drug smugglers. McConnell e-mailed the images to a classified government hotline for whistle-blowers. Then he printed backup copies and, following government procedures for handling classified information, sealed them in an envelope that he placed in another envelope, marked “secret.” He hid the material behind a piece of furniture.