Arthur, Lord Saltire is the ten-year-old son of the 6th Duke of Holdernesse and his wife, Lady Edith. After his parents' separation, his father sent him to The Priory School, an élite boarding school run by Dr Thorneycroft Huxtable. His disappearance from the school formed the central mystery of the "The Adventure of the Priory School", which Sherlock Holmes investigated at the request of Dr Huxtable.