The Champion by Mary Alford

Dr. Aaron Carson’s once promising career as chief of surgery has gone up in flames because the mistakes of his past remind him of the lives he’s failed to save. First his best friend in Afghanistan, and then his wife.
Running away from his failures, Aaron finds himself hiding out from life among the Apache people of northern New Mexico. When a young hit-and-run victim is brought into the clinic where Aaron works, the boy’s death will lead him and Tribal Police Chief Rachel Altaha on a twisted chase into the seedy world of human trafficking to catch a killer.
For Rachel, almost watching a young woman die in front of her is a painful reminder of the one person she hadn’t been able to save. Her best friend from high school. Jasmine disappeared the summer before their graduation and was never seen again. Rachel is even more determined to save the lost young women who have fallen through the cracks of society like she couldn’t save Jasmine.
Working closely with Aaron, Rachel soon learns Aaron is not only her champion, but also the one who donated the money anonymously to save the clinic from closing. As Rachel unravels the secrets from Aaron’s past that brought him here, she feels a connection to Aaron she hasn’t experienced since she’d lost her husband to war.
But with a killer on the loose and his victims mounting, she and Aaron must set aside their hopes for the future in order to bring the killer to justice before he disappears once more into the darkness in which he hunts.