Allison's hollering about how the assisted living facility inevitably kills people, so Tom's handing her a death sentence. Tom's point is that she is not safe on her own and that he and his siblings have decided they don't want her anymore. The actual point is that she needs to be taken care of, and the best way to do that is not in the house where they already have 50 neglected children, most of them miscreants and deviants. I don't even remember what happened to the other twin. And there was that serial killer kid Lynette was hanging around with, too? Did I make that up?
But I think the secondary point is that Lynette never hated her at all, but she gave her so many constant reasons to hate her, even before she started messing everything up, that you could barely blame her if she did. And also that once you've had the "I fixed the boy you broke and now you're fucking him up again" conversation, no matter how satisfying it was (and it was), you can't go back from that. So don't ever have that convo with your own MIL, because now you've created three problems.
But also, it's not the nursing home that kills you, it's the fact that you are wicked old. Symptoms, not syndromes. She tries to set up this false parallel with summer camp, which is more than a little manipulative on the face of it, but really it's just super sad, because the only answer to "When do I get to go home?" is: Not really ever. And this storyline has a lot of dignity in it, on balance, because it's just one more thing of the many Tom/Lynette things where there's no winner, just loser after loser, and I have always loved how they're able to stay married no matter what. They're the only ones that are obnoxious because they're too real.
Mary Alice wraps it up for ya: Tom's Halloween fear is that Allison won't ever forgive him for taking care of her the best and strongest way he can, while Lynette's is that a life without a nanny is worse than even an addled one (which, get ready for a nanny that makes Treetrunks look like Nanny McPhee).
Gabrielle's is that Juanita, whom she's always treated as a stepchild for being fat and is now getting shoved out for not even being legitimately her daughter, will figure it out one day and blow everybody to hell, and she'll be right to do so, because they are screwing that awesome little girl over with both eyes open.
Beth's fear is that Paul Young will murderize her or kick her out of the house before she gets to do whatever Hard Candy situation on him. And Susan's fear is partially that Mike will realize how wonderful life is, several thousand miles away from Susan, and never come back. Yes, Susan is afraid of the world, which is a lonely place, without Mike or Julie to tie her shoes, or a job, or school for MJ now that he's not on teacher-tuition, or a basic understanding of physics. Susan fears many things, because she does not understand many things. But the number one thing Susan fears, deep down where nobody can see it? Megatron, currently hiding on Wisteria Lane in the form of Mrs. McCluskey's sedan.