Deep Canyons: Under Carico's Moons, Book 2

Haunted by her past, Lee Vawn-Cory joins a trek on horseback to explore an unsettled region of the planet Carico. Nothing like hooves on the ground to get to know a place. Then her horses show up at Seth Reilly’s place without her. He sets out to find her, dreading all the things that can go wrong in the wilds. But what he finds is beyond his wildest imaginings. Captured by non-human castaways, he is taken to a hidden enclave where he discovers Lee already being held. It’s not as simple as escaping. The future of Carico depends on finding a path to peaceful contact between the stranded castaways and the planet’s human colonists.