Gray Day

In this book, Eric O'Neill recounts his thrilling experience as a 26-year-old FBI agent tasked with a one-on-one undercover investigation of Robert Hanssen, a veteran agent suspected of spying for the Russians for nearly two decades.

With no training in face-to-face investigation, O'Neill worked in a high-security office to gather evidence against Hanssen while officially helping the FBI secure its computer systems.

The book details the psychological manipulation, power struggles, and the pressure O'Neill faced during this mission, as well as the broader implications of how the United States allowed Russia to dominate in cyberespionage.