The Hound of the Baskervilles

Sir Charles Baskerville died of heart failure induced by fear. He was actually killed by Stapleton, who used the legend of the Hell Hound to terrorize the family. Stapleton released a hound on the moor to intimidate Sir Charles, and the stress of the supernatural legend triggered a fatal heart attack in the elderly man.

Mortimer mentions that Sir Charles died of pure fright, setting up the idea that psychological terror was the weapon.

Stapleton dressed Selden in Sir Henry's clothes to make it appear that the hound had targeted the wrong person. The killer hoped that if Sir Henry were thought dead or that the curse had claimed someone else, the real heir would be lured into a false sense of security. This also explain the missing boot, Stapleton stole it to plant on Selden's body.

Earlier, Sir Henry mentions a boot went missing, which seemed trivial at the time.

Stapleton is actually a descendant of Sir Hugo Baskerville through an illegitimate line. His real name is Frankland, and he is the son of a Baskerville who was disinherited. He and his supposed daughter Cecile plotted to murder the rightful heir, Sir Henry, so they could claim the £1,000,000 inheritance themselves.

Bishop Frankland mentions he studies insects and knows the land's lore, hinting at his connection to Frankland/Stapleton.

The hound is not supernatural, it is an ordinary dog that Stapleton dressed in a mask and illuminated with phosphorescent paint to make it appear demonic. Holmes shoots the hound during the attack on Sir Henry, revealing it to be a regular animal rather than a supernatural creature. This exposes the legend as a deliberate hoax used to frighten the Baskervilles.

The legend speaks of a Hell Hound, but Holmes is skeptical from the start, treating it as a rational case.

Holmes secretly travels to Dartmoor to investigate freely without alerting the villains. He suspects someone at Baskerville Hall is complicit and knows that if the criminals realized he was watching, they would alter their plans. By observing from the hills, Holmes gathers evidence of Stapleton's scheme and positions himself to save Sir Henry during the final confrontation.

Holmes initially tells Watson he cannot travel, then secretly arrives, this deception serves the investigation.

The missing portrait of Sir Hugo Baskerville conceals a crucial clue: Sir Hugo had a webbed right hand, the same physical trait that Stapleton possesses. This proves that Stapleton is a blood relative of Sir Hugo and therefore a descendant with a claim to the Baskerville inheritance. The portrait was stolen to hide this damning evidence.

The Barrymores mention one of two portraits is missing, a discrepancy they claim has persisted for months.

Cecile Stapleton attempts to flee across the Grimpen Mire after Stapleton is killed, but she sinks into the treacherous bog and perishes. Unlike Watson's earlier rescue by Stapleton, there is no one nearby to save her. Her death is the tragic end of the Baskerville line that resorted to murder for inheritance.

Watson previously nearly dies in the Grimpen Mire, establishing its deadly nature.

The tarantula that frightened Sir Henry in London was stolen from Bishop Frankland's collection by Stapleton. Frankland had been blackmailing Stapleton, knowing about his true identity. The tarantula was used as a weapon to create another terrifying incident and reinforce the curse legend, driving Sir Henry toward the moor where Stapleton could finish him.

Mortimer mentions the tarantula threat before they leave London, connecting the London incident to the case.

The Barrymores helped Selden because he is actually Mrs. Barrymore's brother. When Selden signals from his hideout on the moor with a light, the Barrymores supply him with food and clothing out of family loyalty. They are not villains, but their secret aid to a convicted murderer creates suspicion and complicates the investigation.

The Barrymores show nervous behavior when discussing the moor and missing portrait, hinting at their secret.

Stapleton's plan involves luring Sir Henry to the ruins on the moor at night, where the hound would attack him. The legend of the supernatural curse would make it appear the curse had claimed another Baskerville. After Sir Henry is dead, Stapleton (as a descendant) would claim the inheritance through his connection to the Baskerville line.

Stapleton rescued Watson from the mire to get close to Sir Henry and gain his trust.

Holmes shoots the hound to save Sir Henry's life during the confrontation on the moor. By shooting the hound, he reveals it is a physical animal rather than a supernatural creature, exposing Stapleton's hoax. The wounded hound then turns on Stapleton himself, mauling him fatally, an ironic death for the man who created the monster.

Holmes has been secretly observing the moor, waiting for the right moment to intervene.

Sir Henry Baskerville survives the hound attack and inherits the Baskerville estate. The curse is exposed as a fraud, and the true villain, Stapleton, is dead. Back in Baker Street, Sir Henry returns the stolen portrait of Sir Hugo that was found on Stapleton's farm, and he is now safe to claim his inheritance without fear of the supernatural threat.

Holmes protects Sir Henry throughout the case, ensuring he lives to inherit.