Lil and Coop meet when they are 9 and 11 years old respectively. Coop is staying with his grandparents in South Dakota (hence the Black Hills title) while his parents try to salvage their marriage. It doesn't work and he spends many summers and vacations with his grandparents on their farm, learning to ride and track animals and do other things that he doesn't get to do in New York. At some point he and Lil realize that they love each other but Coop breaks off the relationship and Lil is heartbroken.
Coop becomes a cop and then a private detective, Lil earns a doctorate and then fufills her dream of opening a refuge for wild animals. When someone starts shooting animals, and then people, and they realize that Lil is the ultimate target, Coop comes to her rescue and they fall in love again.
Waaayyy too much language and sex!! Rated R.