Lincoln and Clyde are playing video games at the latter's house, when he tells the former about "The 20/20 Rule," so that their eyes aren't constantly looking at the screen. However, when they look out the window, they notice Bobby, and Clyde immediately thinks that Bobby is cheating on her, when they see him go into another girl's house. After Bobby leaves, they go across the street, and ask him what he was doing, but Bobby tells them to not tell Lori he was there, stating it's complicated, and rides off.
Lincoln plans to tell Lori, but when he sees her, she looks so happy talking to Bobby, that he can't bring himself to tell her about what he and Clyde saw. Clyde calls him on the walkie-talkie, but Lincoln says that he couldn't bring himself to do it. Clyde mentions how he feels about Bobby, and the rest of the sisters barge into Lincoln's room, with Lola demanding that Lincoln tell them about Bobby cheating on Lori. After Lincoln explains everything that him and Clyde saw, Lisa points out that while what the boys saw and heard suggests that Bobby's cheating on Lori, they don't have enough evidence to prove Bobby's alleged unfaithfulness. Lana agrees to this, pointing out that a person has to be "a zillion percent sure" of something before telling Lori about it, because she will get furious if she's presented with false information. Lynn vouches by revealing that one time, after she once told Lori that they were out of bread but later discovered that there was still a loaf left in the house, Lori beat Lynn with said loaf.
Sometime later, the sisters (minus Lori) are with Lincoln at Clyde's house, as they stake out to get more info on Bobby. Luna announces to the others when Bobby shows up, and they listen in through a radio link, and notice them seemingly kissing through the curtains. When they exit the house, however, it turns out that the guy kissing Clyde's neighbor was a different person (presumably her actual boyfriend), while Bobby's apparently just friends with the couple. The sisters conclude that Bobby's not cheating on Lori, and get upset at Lincoln for apparently wasting their time.
Later, Lincoln and Clyde are at the mall playing in the arcade, when Clyde brings up the 20/20 rule again. They look away, only to see Bobby in another store, and with another girl. They once again suspect Bobby of being a cheater, just with a different girl, and proceed to try and get photographic evidence before telling Lincoln's sisters again. They follow Bobby around, and see him get into another girl's car, and they proceed to try and get proof that Bobby's cheating. They arrive at a hill, where they take a picture of Bobby and the other girl in the car, and they drive off. Lincoln and Clyde continue to pursue them, eventually Bobby gets dropped off, and they follow him to yet another girl's house. They use the girl's dog to get a camera into the house, and Bobby begins to remove some of his clothing, as this only strengthens their suspicions. They follow Bobby to a café, and they notice him doing a tango with random man. They once again see him with the girl from the mall, and they see them in a jewelry store, and Bobby makes a pose with a little jewelry box, that makes it seem like he's proposing to the girl. They now feel they have enough evidence to prove that Bobby is indeed cheating on Lori, and go to tell the sisters (minus Lori). They feel bad for Lori, as she is ecstatic for her and Bobby's date that night.
They go off to tell Lori, but she's already gone, and they can't contact her cellphone, so Lincoln decides that they need to head over to the restaurant to confront Bobby themselves. They arrive at the restaurant, and question Bobby about proposing to that other girl. Clyde attempts to attack Bobby, but he falls back, and lands against a bunch of food, causing it to fall over on the floor. Lori arrives, and is surprised to see her siblings at the restaurant, and Lincoln tells her that Bobby has been cheating on her, which surprises both Lori and Bobby.
Lincoln presents all of the evidence that they gathered to prove Bobby's cheating on her, but Bobby disproves all of their suspicions. He mentions that the girl from the mall, Dana, is his co-worker from the department store, and explains that she assisted him with the dress and earrings that he purchased Lori for their date. The girl whom he drove around with is a girl named Monica (whom he knows from his tour guide job), and explains that she was helping him out by showing him romantic locations that Bobby can bring Lori to. He says that the older woman whose house he visited, Pam, was fitting him for a tuxedo, and that the man from the café is named Darin, whom Bobby met on the bus, and that he was instructing Bobby on how to dance. Finally, he explains that the first girl, Teri, is his co-worker from the pizzeria, and that she was teaching him how to order food in Italian Mandarin.
Lincoln, the sisters, and Clyde feel bad for thinking that Bobby was cheating on Lori, and assume that Lori will be (understandably) furious for nearly ruining her date with Bobby. However, instead of being angry, Lori appreciates them for trying to look out for her. Everything seems fine until Giovanni mentions how Clyde destroyed the food they had on the cart, and that they need to pay him back for it. Lori and Bobby enjoy their date while Lincoln and Clyde (and presumably the other sisters) work in the kitchen to pay back the owner.
Lily, Monica, Darin, and Teri's boyfriend have no lines in this segment.