Hiro and Baymax arrive at the school lab in time to see Go Go, Fred and Wasabi putting up decorations for Rivalry Week, where San Fransokyo Institute of Technology takes on their rival, the San Fransokyo Art Institute. Every year both schools play pranks on each other. SFAI paint SFIT's dining hall, while SFIT steals SFAI's memorial statue of Lenore Shimamoto. Hiro likes the sound of nerd school mischief, and instantly wants in. This year, they hope to plan the ultimate statue grab. Little does anyone appear to know, however, that Honey Lemon is a part-time student at SFAI, and has been secretly taking art classes. The school is so impressed with her work they decide to put it all on display in the Fine Arts Department Gallery. Meanwhile, Obake is on the school grounds in disguise. He goes to the newly restored house of Lenore Shimamoto to find something. He uses special glasses to scan the house, but his search is thwarted when a child bumps into him and breaks his glasses.
Back at SFIT, Hiro and his friends are going over their plan to steal the statue. Honey Lemon is worried they will find out she has been taking art classes at SFAI. She awkwardly tries to convince her friends to forget about stealing the statue to no avail. Just then, Professor Granville walks in. Instead of shutting them down, she offers to assist them in their plan to steal the statue. By evening, Hiro, Baymax, Go Go, and Honey Lemon sneak into SFAI while Granville, Wasabi and Fred stand guard outside the dining hall, which will be SFAI's target. Sneaking around and avoiding campus security, Honey tries her best to keep her friends from finding out that she has been taking art classes at SFAI, only for her to realize later that Go Go already knows. She heard Honey talk about it in her sleep. Just as they begin taking the statue, security is on the alert. Hiro, Baymax, Go Go, and Honey hide inside Lenore Shimamoto's house. Once the coast is clear, they come out of hiding. Honey accidentally presses a hidden button built into a clock. The living room floor lowers them down into a science lab hidden beneath the house.
The Lab they discover belonged to Lenore Shimamoto, which implies that she was both an artist and a scientist. Honey Lemon finds a shelf filled with books on elements, placed in order of the Periodic table from 1906. She notices that gallium is out of place and tries to correct it. As she takes the book out, she triggers a mechanism which opens a secret compartment on the table. Inside is Lenore Shimamoto's personal journal. Honey secretly takes the journal just as campus security shows up. Pretty soon, news of Shimamoto's secret lab spreads fast. Honey and Go Go return home with the journal, and have a read through. According to the journal, written in Lenore Shimamoto's own words, she kept her scientific work a secret from the public, and in her last entry she made a groundbreaking discovery that could change the world. The rest of the journal is all blank pages, so it does tell them what else happened. Honey notices the last entry was made before the great catastrophe of 1906, implying that the chaos may have ruined her plans and never had the courage to try again. All this mystery of what Lenore Shimamoto discovered leaves Honey and Go Go baffled. Honey plans to solve it.
Meanwhile, back at SFIT, Fred and Wasabi are still on guard, and so far no one has approached the dining hall as of yet. However, they are ambushed by members of SFAI. Professor Granville finds the dining hall next morning, painted with rainbows and fields full of flowers, with Fred and Wasabi tapped against the wall and painted over to look like unicorns. After re-reading the journal, Honey is on her way to hand it back in. She is approached by a man named Mr. Ekabo, who is Obake in disguise. He tells her he is a historian from the San Fransokyo Museum of Art, and persuades her to give him the journal. When she realises she has been tricked, Honey and her friends go after Obake. Since she left her SFIT ID in the journal to use as a book marker, they track Obake to an abandoned warehouse, using the RFID chip in Honey's ID card.
Big Hero 6 surround Obake, who is reading through the journal and has been expecting them. To give him more time with the journal, he traps them in three boxes which contain replicas of Fred's room, Hiro's room, and Shimamoto's lab. Inside each room are timers with a riddle underneath: Fred's room "The hardest thing to face is yourself", Hiro's room "Find the whole solution to your problem", and Shimamoto's lab "Don't ignore the pressing from the wall". Suddenly, the timers start counting down to a minute, activating different traps. Honey and Go Go are in the replica room of Shimamoto's lab, and the walls start to close in. Wasabi and Fred are in the replica of Fred's room, who both fight against clones of themselves. Hiro and Baymax are in the replica of Hiro's room, which starts to take on water. There is no escape for either of them. However, Honey Lemon figures out that all the riddles have a double meaning. "The pressing from the wall" is a play on word for the plant picture on the wall. Honey presses, which stops the walls and opens an exit. Honey passes this onto the others. Wasabi and Fred figure out the best way to defeat their clones is to switch, and Hiro finds a hole that lets the water out. Obake congratulates Big Hero 6 on their performance, and disappears before they can apprehend him. He leaves the journal behind with a message inside that reads "Until next time..."
Later, Honey learns that all her friends knew she was taking art classes at SFAI, and they are okay with it. Meanwhile, Obake returns to his hideout with the pages from Shimamoto's journal digitized into his computer. The blank pages reveal to him hidden contents, formulas and equations.
- Ryan Potter as Hiro Hamada
- Scott Adsit as Baymax, Tour Guide
- Génesis Rodríguez as Honey Lemon
- Khary Payton as Wasabi, Clone Wasabi, Campus Security #2
- Jamie Chung as Go Go Tomago
- Brooks Wheelan as Fred, Clone Fred
- Jenifer Lewis as Professor Granville
- Andrew Scott as Obake
- Diedrich Bader as Bluff Dunder, Campus Security #1
- Jeanne Sakata as Lenore Shimamoto
- Nicole Sullivan as Stern Woman
- James Urbaniak as Art Teacher
- San Fransokyo Art Institute is based on the real San Francisco Art Institute.
- Big Hero 6 meet Obake for the first time in this episode.
- Obake's alternate identity is credited simply as Mr. Ekabo ("Obake" spelled backwards). However, the card he gives Honey Lemon gives him the first name as Herman.
- Fred is seen wearing his mascot costume from the movie.
- This is the first episode where the Disney logo appears above the Big Hero 6 title in the intro.
- The painting Honey Lemon paints and tries to hide at SFAI's student museum is fan art by Tumblr artist Punziella.