From Flushing with Love - S5.E10

Fran and Niles fight over who gets to ask Mr. Sheffield for the weekend off. Fran wins, and Niles accuses her of seducing Mr. Sheffield to get what she wants. He decides to get back at her and allies with C.C. against Fran. Finally, Niles and Fran forgive each other, and he suggests Fran takes Mr. Sheffield with her to the Fine Family Reunion at the Niagara Falls, the perfect place for him to propose and a solution that will give them both the weekend off. Unfortunately, Fran doesn't listen Mr. Sheffield's proposal. He slips and falls, with no recollection of what happened.