Traci begs Gianna to rejoin the Eyeball, clearly hoping to leverage Gianna’s friendship with Dexter for pro-Dexter coverage. Following advice from her mentor at The Pines, author Phyllis Birdwell, Gianna agrees. She reflects that many students have formed friendships with Pines residents: Sophie with former model Edna Khalily, Alex with athlete Cyril DeSouza, and her brother Ronny with the combative Archie, whose boxing sessions have made Ronny less hostile. Gianna sees Dexter pushing Leo in his wheelchair and working on a secret coding project. When Teagan joins them, Dexter chats openly with her, making Gianna feel excluded. Later, Dexter asks Gianna to help him shop for new clothes at the mall. At the mall, full of Pines residents walking for exercise, Dexter is extremely particular about his wardrobe, saying that he wants to look like kids from New York. Gianna realizes that the makeover is to impress Teagan. When they return to The Pines, Dexter immediately runs to show Teagan his purchases without thanking Gianna. Upset, Gianna vents to Phyllis, who asks if she and Dexter are “going steady,” an old-fashioned term that confuses and annoys Gianna.

Grandma Adele wakes Dexter to tell him that Leo has had an accident and is in the hospital. At the hospital, Leo is arguing with a doctor, refusing admission because he must finish the code project for Dexter’s school board meeting in three days. Dexter explains their plan: to demonstrate an unbreakable code at the meeting, with Leo as the expert who cannot crack it, proving the quality of Dexter’s Pines education. Dexter reflects that he is no longer certain he wants to be unsuspended, realizing that he’s come to value his friendships with his school peers.

After Adele convinces Leo to stay at the hospital long enough for a thorough examination, they take Leo back to The Pines. Later, Teagan invites Dexter to visit her in New York and attend a school dance after Thanksgiving. Dexter is excited but wary, remembering her previous coldness. For the final test of their project, Dexter and Ronny create a complex code based on rap song lyrics to encrypt messages. Leo works on it for half an hour before admitting defeat. Dexter feels triumphant but sad seeing Leo look old and tired. After Dexter explains the solution, Leo is delighted and tells Dexter that he would have made an excellent Bunker Boy.

Ms. Napier confronts Traci and Gianna about an Eyeball article calling students to action at the school board meeting to support Dexter. She worries that it will distract from the vote on a new school and could incite a riot. Gianna defends the article, stating that Dexter’s case matters to students. In her office, Ms. Napier congratulates Ronny on a B-minus in math. Ronny credits Dexter for tutoring him and reveals that practically the whole school now visits The Pines regularly. Flabbergasted, Ms. Napier realizes that Dexter is not isolated but the center of a thriving social scene. She tells Principal Dinkins, but he’s only concerned about students disrupting the meeting. Frustrated by his narrow focus, Ms. Napier visits The Pines to meet Grandma Adele. Over tea, Adele says that Dexter is conflicted but that she hopes he returns to school because he has become a new person around his peers. Ms. Napier praises Dexter’s character but warns that the zero-tolerance policy is inflexible. When Dexter arrives home, he is startled to see Ms. Napier. She tells him that she admires him regardless of the meeting’s outcome. An ambulance siren sounds, and they see it stop near Leo’s condo. Dexter’s face drains of color as he breathes Leo’s name.

Dexter runs to Leo’s condo and sees emergency medical technicians carrying Leo out on a stretcher. Leo, weak but determined, tells Dexter that he must go to the meeting and do the demonstration without him. Before being loaded into the ambulance, he assures Dexter that he’s as good as any Bunker Boy. Grandma encourages Dexter to attend the meeting and make Leo proud. Archie drives them to the school, which has a packed parking lot. The meeting has been moved to the gym to accommodate the large crowd. Students greet Dexter with cheers and high-fives. Jackson gives him a strange look when Dexter mentions his special project. Dexter cannot find Teagan, who had agreed to be his demonstration partner. A group of sixth graders led by Allie Westerberg insists on showing Dexter their newly cleaned basement room for a shuffleboard league office. Inside, Dexter spots the words “Welcome to the Bunker” carved into the polished table and realizes that this was the secret WWII headquarters of the Bunker Boys (250). He finds Leo’s initials carved into the table and is overcome with emotion. Back in the gym, Mr. Dunwoody begins the meeting. When Dexter’s name is mentioned, the crowd roars with support. Dexter presents his letter requesting the special project, but Dunwoody declares it a forgery. Devastated but thinking of Leo, Dexter asks to do the demonstration anyway. After the crowd protests his initial refusal loudly, Dunwoody reluctantly agrees. Dexter realizes that Teagan is a no-show, but Gianna calls out from the crowd, offering to be his partner.

Dexter protests that Gianna does not know how to operate the machine, but his grandmother encourages him to accept her help. Dexter gives Gianna a quick tutorial on the GX-4210 coding machine. They successfully demonstrate the code; the decrypted message turns out to be one of Ronny’s humorous T-shirt slogans, which makes the audience laugh, and Ronny proudly claims it. Dexter shares his recent discovery with the board, explaining that the Bunker Boys worked in the school’s basement and that he found their initials carved into a table there. Mr. Dunwoody dismisses this as interesting but irrelevant to the decision about building a new school. Gianna passionately argues that they cannot demolish the school because the bunker is a historically significant site and the town’s contribution to the world. The crowd gives her an ovation. Dunwoody concedes her point, suggesting that the bunker could become a museum within a refurbished school. Gianna argues that all Dexter was trying to do at WEMS was use his unique skills to fix what needed fixing and that his Swiss Army knife is a tool for repair, not a weapon. Dunwoody says that he believes her but that the zero-tolerance policy is absolute. As the crowd protests, armed police officers burst into the gym. An agent announces that the room is on lockdown by order of the Federal Bureau of Investigation (FBI).

Special Agent Corrigan explains that the FBI has tracked unbreakable coded messages to the school and suspects a terror cell. Dexter proudly reveals that the messages were his school project, created using WWII coding machines and T-shirt slogans. Impressed that Dexter’s code baffled the FBI, Mr. Dunwoody offers to reinstate him. Ms. Napier intervenes, asking Dexter what he truly wants and giving him the choice. The gym falls silent as everyone waits for his answer. Dexter reflects on how much he has changed and how much he wants to be part of the school community, especially as the shuffleboard league commissioner. He announces that he wants to come back. The students erupt in celebration, tossing papers in the air. Gianna and Ronny hug Dexter as the student body rushes the stage. Gianna secures the coding machines from damage. Students hoist Dexter onto their shoulders and parade him around the gym. Dexter spots Jackson looking miserable and suspects that he forged the letter. The FBI agents leave. On the way home, Dexter is excited to tell Leo about the FBI and the bunker. When they arrive at The Pines, Felix informs them that Leo passed away at 6:53 pm, around the same moment Dexter discovered Leo’s initials in the bunker.

Dexter attends Leo’s funeral, which celebrates his 99-year life. At Gianna’s urging, Dexter shares how he found the bunker and how their code stumped the FBI, wishing he could have told Leo directly. After the service, Teagan is waiting for them at The Pines. Dexter internally contrasts Teagan’s absence from the funeral and the board meeting with Gianna’s steadfast friendship. When Teagan asks about visiting her in New York for a dance, Dexter declines, realizing that he’s outgrown his feelings for her. On Monday morning, Dexter goes to the bus stop alone, feeling ready for middle school. A brand-new, quiet electric bus arrives instead of the old one. Mr. Milinkovic explains that the old bus is being retired, and Dexter reflects that Leo was right about everything. Students give Dexter a standing ovation. He sits with Gianna, who explains the new buses and other improvements, like astroturfing the soccer field, using money saved by renovating the school instead of building a new one. Dexter sees Jackson at the back of the bus looking unhappy. Gianna compliments Dexter’s new haircut from a professional barber rather than Grandma. Dexter notices a loose screw on a window frame and uses the screwdriver attachment on his Swiss Army knife to tighten it. Mr. Dunwoody had made him remove the blades but allowed him to keep the tool as part of his reinstatement. Dexter embraces his role in helping with the small details during the upcoming school refurbishment.