Corporal Lyons is a British Army soldier stationed at Baskerville Military Base. Corporal Lyons shows Sherlock Holmes and John Watson around the military base. Although he is initially slightly reluctant, he agrees to show them around based on Sherlock's possession of Mycroft's identification, as well as Watson's military rank. He knows almost everything about the Baskerville Military Base, though he shows some suspicion towards the two after they question him on things he expects them to know.