Orphan X by Gregg Hurwitz

'Do you need my help?' It was always the first question he asked. They called him when they had nowhere else to turn. As a boy he was taken from an orphanage, then raised and trained. As part of a top-secret programme, he was sent out to do the things his government denied any knowledge of. Then he broke with the programme, using everything he'd learned to disappear. He wanted to help the desperate and deserving. But now someone's on his tail. Someone who has issues with his past. Someone who knows he was once known simply as Orphan X.