Spots 
Sherlock Holmes turns to stimulants only when his brilliant mind lacks active work. By examining a worn pocket watch, he deduces the tragic life and habits of John Watson’s late brother from tiny scratches, pin-marks, and jewel engravings. Observation combined with logical inference transforms scattered physical clues into precise biographical facts.
Mary Morstan presents a mystery that began six years after her father’s unexplained disappearance. Every year since receiving an anonymous query, a rare and lustrous pearl arrives in the mail without a return address. A mysterious letter now summons her to an evening meeting, bringing a map marked with four signatures.
A swift hansom cab carries Holmes, Watson, and Mary Morstan through dense, murky London fog. Dark streetlamps and twisting alleyways conceal their destination as an unknown driver guides them toward the suburbs. Every turn deepens the atmosphere of secrecy surrounding Mary's unknown benefactor.
Thaddeus Sholto reveals the dark secret connecting his late father Major Sholto to Captain Morstan. On his deathbed, the old major confessed to hiding Morstan’s sudden death and concealing a vast treasure brought from India. His final confession was cut short by the sight of a terrifying face peering through the window.
At Pondicherry Lodge, the locked attic room yields a gruesome discovery. Bartholomew Sholto sits dead in his chair, his face contorted in an unnatural grin caused by a poisoned thorn. The treasure chest has been emptied, leaving behind only a scrap of paper marked with four names.
Sherlock Holmes examines footsteps, roof tiles, and creosote stains to reconstruct the murder scene. He deduces two intruders: a man with a wooden leg and an exceptionally small, agile companion. While official police inspectors arrest Thaddeus Sholto on surface assumptions, Holmes pursues physical evidence left high on the roof.
Holmes enlists Toby, a mixed-breed dog renowned for a remarkably sharp nose. By following the pungent scent of spilled creosote, Toby leads Holmes and Watson across timber yards and suburban lanes toward the River Thames. Logical analysis gains a relentless biological engine on the trail of the fleeing suspects.
The trail ends at the edge of the river, where the suspects escaped aboard a hired steam launch named the Aurora. Holmes deploys his network of street urchins, the Baker Street Irregulars, to search every wharf along the Thames. Unofficial eyes search the waterways while official police remain baffled.
Days of waiting end when Holmes adopts the disguise of an elderly seafaring mariner. Disguised beyond recognition, he gathers vital intelligence about secret repairs being performed on the hidden launch. The game resumes as Holmes, Watson, and police officers prepare a fast riverboat for pursuit.
A thrilling high-speed chase unfolds along the River Thames beneath the night sky. The native islander Tonga shoots a poisoned dart with a blowpipe before being shot and falling into the dark water. Jonathan Small attempts to escape across the muddy banks, but his wooden leg traps him.
Watson carries the heavy iron chest to Mary Morstan, only to discover that Jonathan Small dumped its contents into the river bed. The priceless jewels are lost forever, removing the wealth that stood as a barrier between Watson and Mary. In losing her fortune, Mary gains Watson’s heartfelt proposal of marriage.
In custody, Jonathan Small recounts the true history of the Agra treasure. Decades earlier in India, he forged a pact with three native soldiers to steal a Rajah's fortune, swearing allegiance as the Sign of Four. Betrayed by Major Sholto and imprisoned in the Andaman Islands, Small spent years plotting his vengeance.
A masterclass in deduction, betrayal, and romance surrounding a stolen Indian treasure and a mysterious pact.