Sherlock Holmes and Dr. Watson are summoned to a desperate plea from an old acquaintance, Major John Ross, who has been framed for murder. The victim, a wealthy man named Jonathan Small, was found dead with a mysterious sign etched into his forehead. The case leads Holmes and Watson to a hidden treasure known as the "Sign of the Four," which has been the source of much controversy and violence. As they delve deeper into the case, they uncover a plot that involves the theft of a priceless diamond and a secret society known as the "Sign of the Four" itself. The duo must navigate treacherous landscapes and dangerous enemies to unravel the truth behind the murder and recover the stolen gem. This thrilling adventure showcases Holmes' brilliant deduction and his ability to bring the guilty to justice, all while facing his own mortality.