Mr. Jack Stapleton is the true antagonist of the Sherlock Holmes novel The Hound Of The Baskervilles and was originally a rather innocent-looking former schoolmaster found of chasing butterflies on the moors and pursuing antiquarian interests. Jack is a polite Victorian gentleman on the exterior but this hides a hot temper which reveals itself at key moments. It transpires later in the story that Stapleton—in reality a long-lost relative of Sir Henry's who stands to inherit the Baskerville fortune—is a scheming, manipulative and money-hungry criminal that Holmes and Watson come to respect and fear. His real name is Roger Baskerville.
Roger is the son of Sir Charles Baskerville (Sir Henry's uncle) youngest brother who was also called Roger, the one who took the most after there infamous relative Hugo Baskerville. Who despite what was believed, did not die unmarried in South America. He married a local beautiful woman called Beryl. There he embezzled public money in Costa Rica and fled to England, where he changed his name to Jack Vandeleur. Using his stolen money he funded the school, but a fever broke out killing the tutor he hired and several of the students leading to the school failing.
Now using the name Jack Stapleton he fled with his wife to Dartmoor, where he supported them by burglary, during on such burglary he shot a man who caught him. Discovering that his relative Sir Charles had made a fortune and had returned to restore the Baskerville name, Roger schemed to steal the fortune for himself, using the family legend of the Hound of the Baskervilles which supposedly killed there wicked relative Hugo. Arriving, Roger got himself affiliated with Sir Charles and built himself up as a friend of his, he also learned for Sir Charles other friend and private Doctor, James Mortimer of Sir Charles weak heart. He also forced his poor wife to posse as his sister, as part of his scheme.
Roger bought and trained a large hound dog to attack specific victims in his grand scheme to steal the fortune and kept it hidden in a mine in the middle of the moors, where is cries of hunger and pain could sometimes be heard. He took it out several times but failed to catch Sir Charles each time, leading to multiple people spotting the hound. To increase its ghostly appearance, Roger had it coated in Phosphorus power which caused it to glow. Scheming a new plan to catch Sir Charles, Roger manipulated the local lady Lura Lyons, a woman disowned by her father for marrying without his wishes, and then abandoned by her unfaithful husband. She had turned to Sir Charles in the past for help, pretending to love her and offering help getting a divorce, but had her send a seemingly innocent letter to Sir Charles to meet him outside his estate one night.
Roger then stopped her going, and instead set the hound on Sir Charles, terrified out of his mind by the site of the beast he died of cardiac arrest. However before Roger could follow up his plan, he found out that another closer relative to Sir Charles had been found, a Sir Henry Baskerville. Sir Henry had lived in Canada for much of his life and was returning to England to pick up his family estate and fortune. Adapting his plans, Roger traveled to London. But not being able to risk leaving his wife alone as she knew of his evil deeds, he forcibly brought her with him and locked her in the hotel room they were staying at.
Due to the suspicious death of Sir Charles, Doctor Mortimer had went to visit Sherlock Holmes for help. Seeing this as a threat, Roger spied upon them in disguise, while pretending he was himself Sherlock Holmes to his cab driver to throw off any suspicion and link back to himself. While Sir Henry was staying at a hotel, Roger bribed one of the staff to steal one of his shoes, so he could train the hound to attack him. But as the shoe was freshly bought it was useless, and he had to steal another one.
Returning back to Dartmoor before Sir Henry arrived, he again built himself up as a friendly figure to him, he also tried to build a relationship with Doctor Watson, who Holmes had sent to Dartmoor on the account he was apparently to busy with another case to investigate. However Watson began to get suspicious over how protective Roger was over his supposed sister.
One night thinking he would get Sir Henry, Roger released the hound, however instead of Sir Henry it killed the escaped convict, who was wearing Sir Henry's clothes (his sister being a servant in the household had supplied them) Roger went to investigate the death, but found Watson and Holmes already there (Holmes having secretly been on the scene the whole time and only pretending to be in London to throw Roger off the trail) he managed to pretend his surprise quite convincingly. But with all the evidence, both realized that it was him responsible for the murders, and following examining several pictures in Baskerville Manor, realized he was also a Baskerville. However knowing there evidence would not stand up in court of law, Holmes planned a trap, by pretending that he and Watson were forced to return to London the next morning and encouraging Sir Henry to except the invitation to dine with the Stapleton's.
The temptation being to great, Roger kept the Hound hidden in his old farm houses barn, to release on Sir Henry when he left to walk home. His wife Beryl having had enough of his abuse and evil deeds tried to stop him, but Roger beat her up and tied her up in one of the rooms to stop her warning Sir Henry. Sure enough after Sir Henry left, he released the hound. However Watson and Holmes were lying in wait, and although startled by the beasts glowing appearance, managed to shoot it to death. Hearing the shots and knowing the game was up, Roger ran trying to escape to his lair in the moors. Yet ultimately before either Holmes or Watson could confront him face-to-face he died: having lost his footing at some point in his hidden lair located in the Great Grimpen Mire, which subsequently caused him to drown in the mire. While investigating Holmes and Watson also find Sir Henry's missing boot, several giant cans of meat paste which he fed the dog on, and the remains of Doctor Mortimer's own dog, which Roger fed to his hound.