The Damage Man by Gregg Hurwitz

Once the U.S. government’s deadliest off-the-books assassin, Evan Smoak was known only as Orphan X. He broke free from the Program, vanished, and reinvented himself as The Nowhere Man — the last hope for those with nowhere else to turn.

When Evan has a chance encounter with a desperate father named Rusty, he agrees to help find Rusty’s estranged son, who has fallen in with the wrong people — violent, unforgiving men who will stop at nothing to get their way. What looks like a straightforward rescue quickly spirals into something far more dangerous and personal.

At the same time, Evan is forced to confront the one ghost he’s never been able to escape: the birth father who abandoned him. In a world where every move could be his last, Orphan X will finally have to face the past he buried—if he can survive the deadly present.