The Obsidian Files 9: The Private Investigater and the Missing Heiress. The Obisdian Files, #9

The conspiracy has a final secret. And she's been running from it her whole life. Charlie Shaw is a dinosaur, a private investigator in a world that has forgotten his breed. He's an analog man of shoe leather and whiskey, and he's just taken a case that's as cold as it is dangerous: find Isabella Sterling, a beautiful, terrified heiress who vanished ten years ago. His hunt for the missing woman leads him to a quiet, forgotten town where she's hiding in plain sight.
But he's not the only one looking for her. When a team of ruthless assassins descends on the town, Charlie is forced to blow his cover, throwing them both into a desperate, cross-country chase. She is his client, his mission, and, against all his better instincts, the one person he is willing to die to protect. On the run, their fragile alliance forged in the crucible of shared danger deepens into something more.
As Charlie, the cynical PI, finds himself falling for the enigmatic woman he was hired to find, he uncovers the shocking truth of her past. She isn't just an heiress; she's a living secret, the final, missing key to the entire Obsidian conspiracy. But the most devastating revelation is yet to come. When they finally unmask the ghost who has been hunting her, they discover a monstrous family connection that redefines the very nature of the war they are fighting.
To end the hunt, Isabella must stop running from her own past and confront the sister who wants her as the ultimate prize. The penultimate installment of The Obsidian Files is a gritty, high-octane road trip into the heart of the conspiracy, a story of a world-weary detective and the one woman who gives him a reason to fight for a future he'd long since given up on.