This short story is an episode from the novelette Submissives Caught on Camera.
Four couples in the San Francisco Bay Area who have a private BDSM club hire Dr. Bridget Fox, an indie filmmaker, to make a movie about their club. Dr. Fox grew up and went to school in England. She lived in Hawaii for two years and has two vocations, videographer, and sexual counselor. She's practiced in Canada and the USA for a couple years.
She gets to know the four couples and eventually writes two movies about their relationships and interactions. Their practices involve acting out skits, or scenes, at parties, often with costumes. During the film, they wear masks to hide their identities from the surface world. The Bridget character is based on a real woman who didn't join the club permanently but interacted with them and actually was an amateur filmmaker with a background in the social sciences.
The story shows how individuals who practice BDSM dating and sex do it as different from each other as the normals practice dating and sex. Every couple has an "arrangement" of practices and limits. Every individual person negotiates what their arrangement will be with a new partner as they evolve in their secret underworld.