Jonathan Quinn is a free-lance cleaner working for a shadowy agency known as The Office. His job is to clean up after operations both in the literal sense as well as checking to see how an operation went. He is hired to go to Colorado to check on a fire that killed a man. Quinn is not informed of who the man was or why is is important. His job is to see if the fire was an accident as the authorities believe. Quinn determines that the fire covered up a murder. Quinn reports this to The Office and returns to his home in LA with his apprentice Nat. He doesn't report a heavy silver bracelet Nat finds in the ashes.
Not long after getting home, an assassin attempts to kill Quinn and Nat. They survive but find that The Office is under attack and its operatives are being picked off. Jonathan and Nat go on the run, looking for a place where the unknown enemy won't expect them to go. Super secret agency attacked, operative on the run isn't a new plot but Battles uses it to good effect to get the action going. I'm rather fond of this story line myself.
Quinn gathers clues and begins to uncover a conspiracy of with horrible implications. He appears to be a target but has no idea why.
If you like the Lee Child Reacher and Robert Ludlum Bourne stories then The Cleaner should appeal to you. As with lot of thrillers, you probably want to avoid examining details too carefully and just enjoy the ride. There were a couple of times when I started to think "huh? Why don't they just ..." but I was able to rein myself in.
The conspiracy is indeed horrible, the bad guys really unpleasant, and the plot plausible because you know there are nuts out there who would like to pull off something like it.
This is Brett Battles first novel and already he is working on a Jonathan Quinn sequel. I am putting it on my watch list.