I have always enjoyed this episode. The ending may be a bit weak, but I think it is highly amusing. I love that horrified look on Lily's face when Nicholas starts going crazy.
One other thing about the cast in this episode is that both Arthur Malet and Bernard Fox appeared in one of the funniest episodes of The Dick Van **** Show, "Never Bathe On Saturday" which involves Laura Petrie being stuck in a hotel bathtub because her toe is caught in the drain pipe. Fox plays an overly ambitious house detective while Malet, in age makeup gets one of the biggest laughs ever when as he slowly saws off the pipe to free Laura and Rob asks him if there's a reason why he can't go any faster. Malet, in his typical accent goes, "The very best one. I'm seventy-four years old!"