The Obsidian Files 4: The Blackmailed CEO and the Double Agent. The Obisdian Files, #4

He built a digital empire on secrets and lies. Now, one of those secrets is a gun to his head. Lucas Walker, the disgraced CEO of Cygnus Technologies, is the most hated man in the world. Implicated in the release of the Obsidian nanites, he's a prisoner in his own company, forced by the government to find a kill switch for the global catastrophe he helped create. But as he works to save his legacy, a ghost from his past emerges with a chilling ultimatum: a secret video that proves his willing complicity.
Blackmailed by a shadowy faction, Lucas is forced to play a double game. By day, he hunts for a kill switch under the watchful eye of his government handler. By night, he secretly builds a terrifying new weapon-a nanite targeting system capable of committing genocide on a global scale. His only confidante is Mia Sorensen, the brilliant and beautiful government agent assigned to be his shadow. She is his warden, his protector, and, in the crucible of a deadly corporate firefight, his unexpected lover.
As their professional lines blur into a desperate and passionate affair, Lucas begins to believe he's found an ally he can trust with his life. But when he sets a trap to expose his blackmailer, the horrifying truth is revealed: the ghost in his machine is closer than he ever imagined. The woman he's fallen for isn't his savior; she's his puppet master, the inheritor of a dark legacy with a vision far more terrifying than Reid Jennings's.
Now, Lucas must use the very weapon he was forced to create to fight back, knowing that the woman he loves is the ultimate enemy. The fourth installment of The Obsidian Files is a high-stakes game of psychological warfare, where love is the perfect cover for the ultimate betrayal.