District Ranger Anna Pigeon of Rocky Mountains National Park is going to have wolves in the park. To know what to expect she is sent to Isle Royale in Lake Superior where scientists have been studying the wolves in their natural habitat for fifty years.

But odd things are happening on the isolated island. The wolves are behaving strangely and soon afterward an assistant is mauled to death. Anna knows something is wrong and begins investigating just before another scientist disappears in what looks like a kidnapping, making her inquiries even more urgent...