The explosion of information in the digital age left government agencies like the NSA struggling with bureaucracy and technology to keep up with the changing times. Responding to the challenge, NSA technical director Bill Binney and a small team of code breakers developed ThinThread, an astonishingly effective data collecting and sorting program that also protects privacy. ThinThread’s built-in safeguards would have prevented the massive surveillance methods later exposed by Edward Snowden. Despite its success, ThinThread was discontinued just weeks before September 11, 2001. How did this program work? Who was behind it? Why was it killed off? After Binney and fellow intelligence officials challenge this decision, they find their world upended.