Your step-daughter, the woman that you've been secretly having an affair with for months now, is staying over for awhile.

On the first night of your step-daughter's stay, as soon as your wife goes to bed, you sneak off into your step-daughter's room where she is eagerly awaiting your arrival in some sexy lingerie. She teases you a bit, saying how she knows how hard it was for you to not get turned on thinking about her being right down the hallway before your wife went to bed for the night. How thinking of her is the only way you can even get hard when you're with your wife.