In the novel At Bertram's Hotel, Dr Stokes is a former doctor and neighbour of Emma Wheeling. The title "Dr" is a courtesy one as by the time of the events in the book, Stokes had been struck off the register.
After Emma Wheeling and her husband found Canon Pennyfather unconscious by the side of a road, they brought him into their house at Milton St. John and then called Stokes to have a look at him. Stokes told them Pennyfather had a mild concussion. He would be all right is he was kept lying down in a dark room.
When questioned by the police, Stokes was aggressive, uncooperative and rude. He insisted that he did not "treat" or otherwise attend Pennyfather. He had been struck off and had no right to. He just told them to avoid giving him alcohol and that what they ought to do was to call the police. He did not call the police himself as that was none of his business.
The reason Stokes was struck off the register is not given specifically but Emma Wheeling suggested it was because of his kind heart, doing favours for girls who were "no better than they should be", suggesting illegal abortions. Despite this, the Wheelings continued to use the title "Dr" to refer to him. Even the main text refers to the interview between Chief Inspector Davy, Inspector Campbell and "Dr Stokes".