The Buried: Jonathan Quinn, Book 9

Everything on the job is going as expected. The target has been dealt with, and all that's left to do is remove the body. But a surprise is waiting for Quinn and Nate, one that completely changes their mission. Then when the client who gave them their new orders disappears, they find themselves on their own, with a human asset holding a dark secret that several parties are interested in obtaining, by force if necessary. To keep the asset alive, the two cleaners must stay on the run, but even that doesn't guarantee success. Because no matter how closely a secret is guarded, if enough people want it, it won't stay buried forever.