Rod Serling's narration is notable in this episode because, in addition to opening and closing the show as usual, it also occurs in the middle of the story, to describe how the children spent years happily with their android grandmother and eventually grow up. Other episodes to feature mid-show narration from Serling are all from the first half of season 1: "Walking Distance", "Time Enough At Last", and "I Shot an Arrow into the Air".
They make a fairly convincing pitch here. It doesn't seem possible, though, to find a woman who must be ten times better than mother in order to seem half as good, except, of course, in the Twilight Zone.
The widowed father of three children takes the children to a factory, Facsimile Ltd., to pick out a new robotic grandmother. When she arrives, young Tom and Karen are quickly smitten by the magical "grandmother." But older daughter Anne will not accept her; "Grandma" reminds her too much of her own mother, who died and left her a bitter young girl. Anne tries to run away, into the path an oncoming van which she doesn't see. Grandma pushes Anne out of the way and is struck, saving the girl. Grandma is stunned, but the sturdily constructed robot soon gets up, and Anne grows to love her when she realizes that Grandma is indestructible and will not leave them like their own mother had.
The children grow up and are ready for college, however it's time for "grandmother" to move on to another family as she is apparently not needed anymore. The grandmother expresses her sadness to leave, yet reassures the children that they brought her just as much joy as she brought them, and that, with time, if she keeps being a good grandmother to other children, she will even be ultimately rewarded with the gift of life and humanity. The children say their farewells and "grandmother" leaves the house for good.
Mr. Serling's Closing Narration
A fable? Most assuredly. But who's to say at some distant moment there might be an assembly line producing a gentle product in the form of a grandmother whose stock in trade is love. Fable, sure, but who's to say?
This is one of the few episodes of the series where Serling does not mention the name of the show in the closing narration.