Grover is at a table with a few glasses of shakes when two bullies, "Bri-Dog" and Chet approach him, as seen in . "Bri-Dog" calls Grover "Grove-error" and dumps some shake on his head. While leaving, Chet compliments "Bri-Dog" on coming up with that name and asks just how he came up with it. "Bri-Dog" tells him he got the school's improv group, the Lobster Street Players, to give that to him by way of a threat. Suddenly, someone dressed in a ninja outfit fills a tennis ball machine with spit-balls and starts it up, firing and bombarding the two with spit-balls. Grover witnesses most of what happened. Fillmore and Ingrid arrive on the field to ask questions pertaining to that. "Bri-Dog" decides not to go by that nickname anymore, preferring to be called by his real name, Brian, instead and he'd rather not talk about it. Since he is there too, Grover introduces himself to the two safety patrollers and says he saw everything except who fired the spit-balls. Then, Joseph finds something suspicious that points toward Grover possibly being the one responsible.
In the Safety Patrol Headquarters' interrogation room, Grover confesses he thought about getting back at the bullies and wanted to, but he never really went through with it and he mentions that his record was clean. But Fillmore and Ingrid show him his permanent record file that proves otherwise, that he had served detention. Grover tells them he got himself into detention purposefully, to escape the bullies, as he couldn't bear anymore torment. He also tells them he has a fear of non-dairy whipped cream, which is what Wilbur happens to use.
After Fillmore, Ingrid, and Vallejo eventually figure out that Grover, Wilbur, Stella Valenzia, and Becca Embarcadero spent time together in detention one Saturday when they decided to team up to take down the bullies, and that it is Stella who is the most likely suspect, Horace mentions he has a computer system with a security camera that can pinpoint who is behind everything. Once the camera focuses on Stella, Fillmore and Ingrid approach her, and off she ran. They go after her through the school's hallway, as the X Middle School Knitting Team are about to begin the quilting contest. Stella winds up entangled in a large yarn ball, rolling into the Converted Center Control Room, where the yarn ball loosens and she is freed. When Fillmore and Ingrid get there, they find that she, Becca, Wilbur, and Grover had taken Horace hostage, as requital for how he treated them. Just as Wilbur is about to damage to control panel by pouring gumbo onto it, Fillmore tells them that there are other, better ways to solve problems with bullies. They say they were only trying to make a right, but Fillmore says they're just as much of bullies as well, that what they are doing isn't the proper solution, and that they are better than that. They seem to listen to and heed his advice. Everyone in the control room hear Principal Folsom announce the quilting contest winner as they watch a monitor. Grover and the three others serve detention time once again, as revealed in the X Middle School Examiner.