It turns out Nathan is allergic to gluten. "Great, I'm a nerd with food allergies. Line up, ladies!" he laments. He’s afraid it'll be too hard, but Will decides the Keens should all do it, as an exercise in discipline. Theresa doubts he can do it. Will senses a challenge. The competition is on. Will just needs to find out what gluten is. Turns out it's in just about everything. But Will plans to teach Nathan discipline while also besting Theresa if it's the last thing he does. And it might be.
Craig and Kenny have their own issues. They’re currently flirting pretty hard with the pair of ladies who work the drive-thru at Big Burger. They're inspired by Will’s discipline. "Perhaps we should show a little discipline and go there more often," Craig suggests. "That's discipline. Doing what you want but doing it all the time. Look it up.”
By the end of the day, Will's cheating on the diet. So he's effectively lost the bet with Theresa -- but only if she finds out. So he heads to Grant's for some gluten-free coaching. When Grant gets up to start cooking, Brenda shows him the stash of gluten-full snacks she has hidden throughout the house. She’s been lying about eating gluten-free for a while now. "That couch alone has so much pie under it it's like a county fair," she explains.
Craig and Kenny head back to Big Burger, but this time, it's not so sweet. The girls are flirting with another pair of patrons in the very same manner. Not cool. Also not cool, even though Will thinks it is: Will's man cave, which is a small, half-dug hole in the basement where he eats whatever he wants. The boys assure him that it needs a lot of work, and that it could even be dangerous, a fact hammered home when Craig gets bit by a huge, nasty spider during his visit.
Will decides to tell Theresa the truth when he gets home. But instead, he gets home to find Theresa eating food out of the trash - she's cheating too. They still have a problem: How to eat all this gluten in front of Nathan, who’s doing a project on gluten for Science Club. So now they’re competing to see who can lie to Nathan the longest. That's just good parenting.
Kenny and Craig show the drive-thru girls they have options too. Not with other women of course. But they hit the Big Burger drive-thru with food from other fast-food joints. After a jealous spat, the boys take action -- they whisk the girls right out of their respective drive-thru windows. Those windows are pretty small though, so it’s not without a struggle.
Meanwhile, Will and Theresa lie to everyone in Nathan's classroom about giving up gluten, until Lucy cracks and confesses she's been cheating on the diet. Then Theresa comes clean. And then so does Will. Nathan's disappointed, but at least he learned that he can be more disciplined than the rest of his family. In the audience, Grant spills his guts to Brenda about eating some cheesy bread. Brenda accepts his confession. Silently.