Red London by Alma Katsu

CIA agent Lyndsey Duncan's newest asset might just be her long-needed confidante...or her greatest betrayal.
After her role in taking down a well-placed mole inside the CIA, Agent Lyndsey Duncan arrives in London fully focused on her newest Russian asset, deadly war criminal Dmitri Tarasenko. That is until her MI6 counterpart, Davis Ranford, personally calls for her help.
Following a suspicious attack on Russian oligarch Mikhail Rotenberg's property in a tony part of London, Davis needs Lyndsey to cozy up to the billionaire's aristatic British wife, Emily Rotenberg. Fortunately for Lyndsey, there's little to dissuade Emily from taking in a much-needed confidante. Even being one of the richest women in the world is no guarantee of happiness. But before Lyndsey can cover much ground with her newfound friend, the CIA unveils a perturbing connection between Mikhail and Russia's geoplitical past, one that could upend the world order and jeopardize Lyndsey's longtime...