Sherlock Holmes is called upon by Inspector Stanley Hopkins to investigate the gruesome murder of Peter Carey, a retired sea captain known for his violent temper and mysterious past. Carey is found dead in his garden cabin, impaled by a harpoon. As Holmes digs into the case, he uncovers a trail involving a secret visitor, suspicious documents, and a shadowy connection to Carey's seafaring days. The deeper Holmes goes, the more tangled the mystery becomes, with clues pointing to a long-forgotten voyage and hidden motives.