X Middle School's bathroom renovation project teeters on the brink of disaster as the new tagger "STAINLESS" strikes at will. Out of leads, Fillmore and Ingrid turn to Randall Julian, the former vandal "FLAVA SAVA", currently in solitary detention. His help puts them back on the trail, but Randall escapes, forcing Fillmore and Ingrid to hunt down both "STAINLESS" and "FLAVA SAVA" before they strike again.

Mrs. Cornwall's pre-algebra final exam looks like it's going to be a tough one. However, some of her students have decided to take more extreme measures beyond studying. Fillmore sleeps over in the school to safeguard the exam, but an unexpected blizzard leaves him standing alone to face a desperate gang of determined exam thieves.

Mrs. Lawson's field trip to the Modern Contemporary Natural History, Art, Science and Miniature Museum takes a horrifying turn as someone draws a mustache on the priceless painting "The Lobster Man at Port". Fillmore, Ingrid, and O'Farrell work to find the culprit and save the painting, but the clock is ticking and everyone's a suspect.

X Middle School's best hope to break a losing streak is Checkmatey, a flamboyant rapper who is X's finest chess player. However, Checkmatey is kidnapped before the championship match, and multiple suspects possess a suitable motive for the crime. Fillmore and Ingrid are on the case—but the clock is ticking down and Checkmatey is nowhere to be found.

The heat is on from Student Council Representative Peabody to get illegal term papers off the street, but the perps always seem one step ahead of the Safety Patrol. After a botched raid and the sabotage of his bike, Fillmore turns to Sonny Lombard, his old partner from his bad-boy days. They track the papers back to Rudy Teravall, the Kingpin of Home Economics, but just as Fillmore and Ingrid get ready to move in on Rudy's gang, Peabody gets tipped off about bootleg hall passes in Fillmore's desk, resulting in Fillmore getting suspended from the force. Nonetheless, Fillmore is determined to find the term papers—with or without his badge.

X Middle School has gone Canada Crazy, and the ambassador is staying over along with his assistant Penny Madrid, who happens to be an old partner in crime with Fillmore. Winston Kotter, the Canadian ambassador, turned Penny around just as the Safety Patrol turned Fillmore around—but Fillmore can't help suspecting something's up, especially as a huge supply of counterfeit baseball cards appear. However, as Winston has full diplomatic immunity, safety patrol investigation is strictly forbidden.