Back in the Game Again by James K. Wilson

After a life of clandestine activities for the US Government, Nathan Green reluctantly is coaxed out of retirement by former colleagues to join their new company, formed to provide outsourced intelligence services. He is soon caught up in a spiraling storm of activity when the operations manager of a French utilities company is kidnapped and held hostage by terrorists in exchange for spent nuclear fuel with which to make a dirty bomb. While in the process of finding and freeing the family, Nathan and his team uncover a far broader plot to terrorize major European cities. In a race against time, Nathan’s team must thread together the seemingly contradictory pieces of a complex puzzle to prevent a catastrophic series of events throughout the Continent.