James Windibank is the antagonist of the Sherlock Holmes story A Case of Identity. He is the stepfather of Mary Sutherland and a rich con man.
He has only just arrived in England and he has just married into the rich Sutherland family. He has a possessive grip on his stepdaughter Mary, making her call him "father" even though he's her stepfather, and he is very stern, not letting her even go to parties on her own.
Soon after James marries into the family, his stepdaughter Mary meets a young man at a gasfitters' ball, whom she falls in love with and he takes her on romantic walks and woos her successfully. The man, Hosmer Angel, was said by Mary to be perfect and a gentleman. After a few romantic trips, Mary and Hosmer proposed to each other, and they got engaged to be married straight away. Afterwards, on the day of the wedding, Mary and Hosmer got separate cabs to the church, but when Hosmer's cab pulled up, nobody came out, it was empty.
This got to the attention of Sherlock Holmes, because he was puzzled about how a man could vanish from a moving cab. Sherlock Holmes was puzzled by the events, such as why an overbearing father would suddenly let his stepdaughter attend a gasfitters' ball, meet a man, and what's more, although her stepfather was out of the country in France when Mary proposed, he was suddenly delighted at the news, but devastated when Angel didn't show up to the wedding. James told a heartbroken Mary that something must have happened to Hosmer, such as arrest or murder, and she went to Sherlock Holmes for help. However, Holmes was intrigued by such a story, and decided to analyse it all scientifically. He was especially interested in how one could disappear from a moving cab. Mary told Sherlock everything that had happened, which puzzled him because James Windibank was a very protective father so why would he suddenly let his stepdaughter get in a mess like this.
So Sherlock Holmes analysed the case with Watson, and they both visited James Windibank himself, who seemed rather pompous but a generally good-natured man. James Windibank expressed his concern for Angel, to which Sherlock said there was no such person. James Windibank answered if they were here to waste his time he would kick them out. Suddenly Sherlock Holmes said he had found the culprit, which shocked Windibank. He asked who the criminal was, and Holmes admitted it was James Windibank himself.
Holmes said that there were plenty of clues: James Windibank claimed to be a overbearing father, so what he actually wanted was for the fortune he had made by his business to never disappear, he feared if his stepdaughter married she would make him lose his money, so he donned a disguise, seduced his daughter at the ball, where it was implied they kissed or made out, and took his stepdaughter on romantic walks to seduce her. Finally they proposed, and James Windibank was engaged to his own daughter. Holmes said that another thing that he worked out as a clue was how James' wife was overly zealous about her daughter's marriage to Angel, as if she fancied him too. However, Holmes said, at the last moment, James Windibank shed his disguise and slipped out of the cab he was in travelling to church and snuck into a cab right beside it. Holmes admitted it was clever, but risky.
James Windibank knew his cards were up and he confessed to all his crimes, but he said that due to his, James', position, Holmes was the real criminal. But Holmes said because of his actions Windibank deserved the rod more than any other criminal he had met, and reached for it, but a scared Windibank fled comically down the street.