Cloe! I have always wondered if perhaps the sirenes the ancient Greeks spoke of were not really mermaids luring saliors to their doom so they could have them underseas as lovers???
A variation, make the receptionist Wendy. It is her first job after Boarding School. When she makes application for the job, the Dr. takes one look and feels he must have her. The first patient is Nanny's sister on her first appointment. The sister and Wendy know each other. The Dr. suggests that Wendy come into the treatment room as having someone there that she knows and trusts will help her relax and make the treatment more effective.
Of course he places both girls deeply under. (After all, we are writing fiction not a term paper) Several things occur to me at this point, he could convince them that they were alone and have each relive the most vivid sexual experience they had ever had, or that they were alone and begin self gratification.
He plants the suggestion in the sister that a craving for a smoke will be translated into intense sexual desire and increased sensativity of both nipples and clit.
In Wendy he places the suggestion that every time he comes out of the treament room into her part of the office her desire will mount and will not abate.
Soon she is rubbing her breasts when alone, then her sex. Finally at the end of the day, he comes up beside her chair and puts his hand on her shoulder. She takes his hand and places it on her breast.......
Siser, meantime, has gone to Wendy's home to see Nanny. By this time her sexual appatite has become huge from the implanted auto-suggestion. Nanny is not there but Frank is. Need I say more?