After a sleepless night of wondering if the obviously true thing could possibly be true, Tom decides to broach the concept of senile dementia over breakfast. It's sad. His mom's like, "I'm not scattered, but thanks for worrying. Remember all these minute details of your childhood and how you hated summer camp and called me on the phone?" Of course, things take a turn for the weird: It seems she didn't really put his puppy on the phone, just barked a couple of times. Then she demonstrates what that was like. An elderly woman at your breakfast table, barking like a dog, in her housecoat. Yeah, she's doing great.
Tom points out to the creeping, eavesdropping Lynette that everything is clearly fine. Lynette, though, has been visiting with her version of Dr. Feelgood, WebMD, and has learned about this thing "sundowning" where people with dementia sometimes only get confused at night. That is very scary and something I didn't know, so thanks for that horrible concept in my head, show. Tom turns it around on Lynette, pointing out that she's wanted Allison out of the house since she showed up.
Instead of pointing out that he totally ambushed her by bringing his awful mother to come live with them, and meddle with Lynette's semblance of a parenting system, and cater to his every whim, and that they have a super creepy relationship that somehow traverses the innate shittiness of Baby Boomer guys and heads into Coming Of Age In Samoa territory, Lynette just makes more lists. "You think this is a tactic? The other day she made tea, then left the stove on for an hour!" Lynette points to the mounting tea-related evidence and suggests taking his mother to a doctor, which is where Tom draws the line.
"We will be denying my mother the urgent medical care she needs, and we will continue to endanger our children! End of discussion!" Which, first of all Lynette does not end discussions, ever, and secondly: You just ensured that if the evidence doesn't suffice, Lynette will totally end up framing Mommy with some kind of Gaslight scenario. Then, once she's made grandma look pathetic and crazy as possible, she'll wash her hands of the whole thing and demand some gratitude for once again helpfully ruining your life. Obviously. Maybe Tom's the one with early-onset, because that is clearly the only option he left his wife.