Call of the Forbidden Way — Robert Owings

When Carson Reynolds gets hired to produce a documentary film at a gathering of Native American medicine men, he never suspects it will be a portal into a world that will radically change his life. Despite his resistance to the Call, he is ineluctably drawn into a realm of shamans, priestesses, deities, and plant-medicine work, where he becomes engaged in a searing struggle with extra-dimensional forces that threaten the future of humanity as we know it.