Lestrade - Knew only the two detectives, and he revived both Sir Henry, after his scare from the dog, and Beryl, after being found abused into unconsciousness. He does not provide many of the facts, for he is merely the officer that brought the warrant for the arrest of Stapleton.
Mr. Barrymore - As a staff member of Baskerville Hall, he met most of the witnesses who Sir Charles and Sir Henry have invited into the hall. However, he directly provided food to an escaped convict on the orders of his wife, but he redeemed himself by informing Watson of the mysterious "L.L." letter.
Mrs. Barrymore - Though she knew nearly nothing concerning the death of Sir Charles, she aided her brother, Selden, while he was starving on the moor, hiding from the police. She convinced her husband to bring the food she cooked to Selden often, even though Mr. Barrymore was well aware of Selden's brutality and viciousness.
Dr. Mortimer - Knew the Stapletons and Baskervilles very personally, being their close friend and neighbor, and he prompted the case to Holmes and Watson. He did not suspect anything of them, and he provided information to both sides, intentionally and unintentionally, ultimately swaying the scales of the case.
Mr. Frankland - An elder over-obsessed with British law, he put his nose in business it should not be in. He sighted Cartwright, believing he was helping Selden, and he pointed the boy out to Watson on the moor. He is also Laura Lyon's father, and he cut all ties from her when she married a man without his consent.
Laura Lyon - She was influenced by  Mr. Stapleton on the terms he would marry her, but she was deceived by Stapleton, accidentally putting into motion Sir Charles's murder. She needed money, and Stapleton convinced her to meet Sir Charles on the moor, but then immediately ordered her not to so Stapleton could unleash the hound upon Sir Charles.
Sir Henry (Me) - Being the victim, he was very thorough in his factual information. He knew Beryl, who he loved, and Jack, who interfered with his love. He was very distraught after the hound attempted and failed to kill him, so it was very hard for him to recall some of the said information.
Mr. Stapleton -
Mrs. Stapleton - Warned Sir Henry to stay away from the moor and Devonshire in general multiple times. She was abused by Jack, and she was found beaten unconscious and wrapped in tape around a crossbeam. She wanted so much to leave Jack, but was so scared of him that she kept quiet.