The Patriot Paradox. The Reluctant Hero, #1

Kurt Vetter was a creature of logic, an analyst who kept the Agency's secrets buried in data while his brother Mike did the dirty work. That carefully ordered life shatters when a package arrives from his brother, sent just before his murder. Inside is a memory card that acts as a blueprint for a global catastrophe. The files expose a terrifying vision of salvation: the engineered collapse of the Russian Federation, triggered by a rogue faction of American patriots using a stolen nuclear asset.
To stop the fallout, Kurt must trade his terminal for a sidearm and step into a world of shadows. His only ally is Amanda Carter, an operative as inscrutable as she is lethal. From the streets of London to the frozen reaches of Moscow, they are hunted by an elite cell tasked with erasing every loose end. As the clock hits the red, Kurt is forced to confront a brutal reality. To save the nation, he must become the kind of man his brother was and the kind of man he always feared he would be.