Through Dark Spaces — Karen Hall

When Hannah Morrison takes an environmental consulting job at a South Dakota surface mine, she doesn't expect to have to confront her darkest, most personal fears. In the course of her work, as she discovers secret after secret, Hannah realizes that somebody is poisoning the water in the beautiful Black Hills. Who--and why? Driven to solve the problem and find the people responsible, Hannah finds herself deep underground, trapped in the darkest of spaces--with a murderer.