Unshaken. The Entire Saga - Jennifer Kay Rice

In a rural area outside Little Rock, Arkansas; a kind-hearted psychologist helps to rescue a woman who has been imprisoned for 33 years. From ages 14 to 47, Kassidy has been isolated from the world. She is behind on world events and modern technology. Malachi bonds with Kassidy and takes her into his home. Malachi, who has a sad history with his own now-estranged family, later adopts Kassidy and makes her his daughter. Kassidy now has the father she has long dreamed of having.
As Malachi and Kassidy try to build a life together, they find themselves having to dodge thunderstorms and roadblocks. They battle Kassidy's biological father and brother, who want to rescind the adoption; Malachi's estranged daughter arrives to demand her inheritance after learning of the adoption and will change; and Malachi is terrified when Kassidy goes missing for two days.
Just as Malachi and Kassidy seem to finally be out of the woods, a shocking diagnosis changes their lives and tests their bond to the limits.