A genetically-enhanced deer, Nadare, is attacking forest workers. In the past, the deer was befriended by a young doctor and treated as his own sibling. Wishing Nadare was intelligent enough to talk back, the doctor convinces Black Jack to move Nadare's brain from his skull to his chest, allowing it to grow and make him smarter. In the present, the doctor who owned the deer must stop Nadare who, out of control from his own intelligence and emotions, attacks his fiancé. They drive Nadare off, and Black Jack operates to save the woman's life.