A prequel.
"Lance Spector is doing something he shouldn't be. He's sleeping with his handler. Here are all the reasons that can go so wrong. Set two years before the events of Book 1, The Center gives a shocking view of how far the Russians are willing to go to get kompromat on a trained assassin. It also shows just how far Lance Spector is willing to go to resist that kompromat, and how his relationship with Levi Roth became so fraught all those years ago."