The final episode of the series finds Hal (David Doremus) and Butch (Trent Lehman) building a replica space capsule. Prudence (Kim Richards) feels left out and their father Professor Everett (Richard Long) agrees its too dangerous for her to be around. The postman (character actor Don Beddoe) brings a package for Nanny (Juliet Mills) that came from England. It is a porcelain doll named Felicity (which translates to happiness) that was Nanny's as a child. Nanny gives it to Prudence to play with. Prudence begins talking to the doll, and suddenly starts saying English sayings and singing old English folk songs. The professor questions her about it and she says the doll talks to her, and he takes it away from her so she can visit her friend overnight. The boys examine the doll and end up breaking it. In what is perhaps the biggest suggestion that Nanny indeed has magical powers, when the professor barely touches the kitchen table, a saucer shoots across to crash on the floor and break. Meanwhile, the boys sneak off to Trimble's doll shop and repair. Mr. Trimble (Walter Baldwin) and Mrs. Trimble (Edith Evanson) say they are unable to repair it. When Prudence returns home, the boys try and stall her, and then a mysterious occurrence takes place.
Reflecting upon the series, "Nanny and the Professor" grew to become more enjoyable for the characters than the content itself. On the classic sitcom spectrum I think the series most aligns with "Father Knows Best". In both, the father is the dominant head of the household of three children with most episodes light on comedy with an emphasis on moral lessons. Yet, as a fantasy/supernatural sitcom, it clearly showed its inspiration of "Mary Poppins". The acting was just fine, but too often it seemed they had little to work with in way of script. Comedy from a nosy neighbor, executed so well on "Bewitched" had its moments here, as did times they gave young Kim Richards some comedic lines. Outside of that, I find the comedy rather light. Some of the moral lessons hit the mark, but for the most part not to the degree of other series. In a word, this lighthearted show is "charming".