I decided not to return to the shop for a few days. Firstly because I had by now ordered a large strap-on dildo and two vibrators from an internet site and I wanted to have the dildo with me when I returned. Secondly I wanted Lisa to have plenty of time to think about the challenge she had thrown down; so when I returned to the shop she would be sure of what she was doing.

When I did finally decide to go, I again left it late in the day. I wanted Lisa's mother to be able to close the shop, if things went the way I planned. I...