Hellbent (Orphan X 3) by Gregg Hurwitz
When there's nowhere else to turn. . .
His name is Evan Smoak. Taken from a group home at age twelve, he was raised and trained as an off-the-books government assassin: Orphan X. After breaking with the Orphan Program, Evan disappeared and reinvented himself as the Nowhere Man, a man spoken about only in whispers and dedicated to helping the truly desperate. Now, the person in need of help is Jack Johns, the man who raised and trained him, and the only father Evan has ever known. Secret government forces are busy trying to scrub the remaining assets and traces of the Orphan Program and they have finally tracked down Jack. With little time remaining, and an elusive new enemy on his trail, Jack gives Evan his last assignment: to find and protect his last protégé and recruit for the program--or die trying.