Adam just wants some adventure back in his life.
That's why he fantasizes about his babysitter, Willow. She always flirts with him, and she always wears such sexy clothes.
So Adam, driven by desire, pretends to forget his wallet back at home so that he can be alone with Willow. When he finds her in nothing but her underwear in his front hallway, he knows she's been having the same fantasies.
He just wants to know if hers have been as rough as his.