Junkyard Dog (Hellhounds Book 1) by Katja Desjarlais

She came looking for a stray. She found something far more dangerous.Joshua Tree National Park Ranger Charlotte has been tracking a large, wild dog for three weeks, one that's already caused a car accident and disappeared without a trace. Armed with a bowl of dog food and more patience than sense, she heads back into the park to find it.Alex is also back at the scene, and he's not there for the view. A hellhound on a mission from Hades, he can't afford to be noticed, let alone followed. He especially can't afford Charlotte. The attraction is immediate and inconvenient, and she's exactly the kind of distraction that gets a hellhound killed.But as bodies pile up in the park and Charlotte gets closer to truths she was never meant to find, Alex has to decide how far he'll go to protect her and whether the man he's becoming is worth more than the mission he was sent to complete.