This time, the children's parents have gone on vacation to New York, and it is up to Uncle Erik to take responsibility for his nephews and nieces, or at least try to. Everything seems to be going well, until Jan and Michael take a little drive in their father's new sports car. The mechanic's bill comes to $30,000, so the children persuade their uncle to open a hotel in their own house. The hotel quickly fills up, but not all of the guests are easy to please. And the strict Mrs. Flinth is definitely not happy with the children's successful hotel business!