Oath of Loyalty: Mitch Rapp, Book 21 by Vince Flynn and Kyle Mills (HC/DJ)
This fragile détente holds until Cook’s power-hungry security adviser convinces him that Rapp has no intention of honoring their agreement. To put him on the defensive, they leak the identity of his partner, Claudia Gould. As Rapp races to neutralize the enemies organizing against her, he discovers that a new type of assassin is on her trail.
Known only as Legion, the shadowy killer has created a business model based on double-blind secrecy. Neither the assassin nor the client knows the other’s identity. Because of this, Legion can’t be called off nor can they afford to fail. No matter how long it takes—weeks, months, years—they won’t stand down until their target is dead.