In the short story The Submarine Plans, Sharples is the country home of Lord Alloway. Poirot and Hastings are summoned there in the middle of the night when plans of a new submarine kept at Sharples were found to be missing. Present at Sharples at that time was a house party comprising the family of Sir Harry Weardale, the First Sea Lord as well as one Mrs Conrad. The latter was a society woman who circulated widely in diplomatic and government circles and had attracted the attention of the secret service. Alloway told Poirot that he had invited her to Sharples so that she might be observed "at close quarters".
The location of Sharples is not given but Hastings records that they got to Sharples from London by car in just under an hour.