Colorado Bodyguard

This is an Apple Books audiobook narrated by a digital voice based on a human narrator.
The rugged terrain of Colorado wouldn't make their mission easy. Nor would the attraction between them. 

Sophie Montgomery's sister was missing and her trail stopped dead in the Black Canyon—which was firmly in Rand Knightbridge's jurisdiction. Part of the Ranger Brigade, he could lead Sophie on a search deep into this remote part of Colorado. Although afraid to disappoint the desperate beauty, Rand couldn't ignore her determination. But it was clear she needed protecting after shots rang out and Sophie barely escaped with her life. Now, as the job he'd reluctantly agreed to became a very personal mission, Rand knew he'd do anything to bring Sophie's sister home. Because seeing Sophie happy was the only outcome he'd allow. Or accept.