The episode opens with sad reminders of good times past. As old-timey music plays the camera pans across paraphernalia from the 30s, finally stopping on a photograph of a young woman-
The next morning Grandma complains to anyone who'll listen about how awful being old is, and how when she was young she never took time to consider this time of her life. Her frustration drives her to try and move across the room without her walker, which leads to a near-fatal fall. Her son and May try to broach the subject of moving her into a home, but grandma's having none of it!
This leads to an awkward scene that night, as a salesman comes by to give a slideshow about how wonderful 'Tranquil Gardens' is. The family tries to put the best spin on things, but Grandma can't help but feel like they're trying to abandon her. They're able to pressure her into signing herself into the home, but nobody feels great about it.
The family tries to put the best face on the upcoming change by offering to let her wish for whatever she wants in the upcoming week. Grandma responds that she does have a wish, but she's not going to tell them what it is! Because it's sinister!
The elements of the wish start showing themselves almost immediately - May trips while waxing the floor, and finds herself having trouble walking around the house! Which suggests that Grandma wanted them to know what it feels like to be old and useless. This supposition is backed up when dad starts forgetting to buy groceries, and Greta pulls her neck while practicing a simple gymnastics flip. How does Grandma react to all of this?
The next day Dad has injured himself, and Great is stuck in a neck brace. Even worse, May's hands are covered with liver spots! She struggles to get rid of the evidence of age with vanishing cream, but the message is clear - some supernatural force is causing the family to suffer all the torments of the aged!
That night is their last evening together, and everyone gathers around the table to enjoy a celebratory dinner. The family all asks what her last wish was going to be, but grandma remains silent on the matter, preferring to look on with a sense of self-satisfaction as her family members are reduced to doddering elderly fools.
So there's the moral of the story, folks - don't put your old relatives in a home. Murder them in their sleep before they can use their dark magic to kill you.
Also, I checked the credits to identify the actor playing the Salesman, and it turns out that the reason I recognized his voice is because it's a super-young Greg(ory) Itzin, beloved character actor who generally plays slimy authority figures, most notably President Logan on 24! It seems he's been doing that longer than I would have imagined!