Tessa is a dom hired for a session to belittle her sub and make him worship her. But she doesn't realize the tables are going to be turned on her. He was highly attracted to Tessa when he booked the session, it's just that he likes to be the one in charge. He uses his mental powers to mesmerize Tessa and make her obey commands while in a trance. Tessa is now the one calling him "master".