as he waits for the train to take him to a weekend party in the country, the narrator notices that gilbert long seems much more assured and lively than before. he also sees that mrs. brissenden (nicknamed "mrs. briss") is much younger-looking than her husband, though she's actually ten years older. the narrator begins to theorize that long and mrs. briss are getting their vitality, vampire-like, from the "sacred fount" of their sexual partners' energy. at first, the narrator theorizes that the source of long's newfound assurance and intelligence is a certain lady john.