How do you spy on a spy? In the case of Senate investigators, you do it by adopting some of their methods. During the five year investigation into the CIA interrogation and detention program, members of the Senate Intelligence Committee, working in a windowless room at the spy agency’s headquarters, suspected that key documents had been removed from their computer network. Luckily, they had a hard copy. To keep it from being destroyed, Senate sleuths spirited the document from the CIA and put it in a safe in the Hart Senate Office Building. The move set off a chain of events that broke open on the floor of the Senate on Tuesday as Sen. Dianne Feinstein, the chairwoman of the intelligence committee, accused the CIA of spying on her investigators. CIA Director John Brennan insists the CIA isn’t trying to thwart her investigations. The Justice Department is now conducting two inquiries: one looking into whether the CIA illegally snooped on congressional investigators and another looking into whether those investigators broke the law. The accusations include lying to Congress and to the Justice Department, and spying on congressional investigators to hide what the CIA was doing. Frank Underwood will no doubt be weighing in soon.