The Cleaner by Brett Battles

Jonathan Quinn is a "cleaner". He works for the Office--investigating or cleaning up messes (disposing of bodies). He's called to Colorado to check out a possible arson case in which a man died. Soon after, most of the members of the Office are killed and Quinn and his apprentice, Nate, are on the run. They hide out in Vietnam with an old female colleague of Quinn's named Orlando. While there, Quinn is trying to figure out who wants him dead and why. Soon, he stumbles upon a threat from a very formidable adversary and he realizes he must organize a mission to take him down. The Cleaner is a non-stop around-the-world adventure that is reminiscent of the novels of Lee Child.