When Eric O'Neill is promoted from a low-level surveillance job into the headquarters of the FBI, his dream of becoming a full-fledged agent is on the verge of reality. He is hand picked to work for the renowned operative Robert Hanssen within "information assurance," a new division created to protect all classified FBI intelligence. Eric quickly discovers the true reason for his hire: Hanssen is the sole subject of a long-term, top-secret investigation, a suspected mole made all the more dangerous by the sheer global import of the information he is charged with protecting. The Bureau asks Eric to slowly draw the traitor out of deep cover.