Alistair Krei is in his office at Krei Tech Industries having sushi, served by a professional chef named Momakase. As he feasts, he realizes too late that his food has been poisoned, and becomes paralyzed. Momakase also turns out be a master thief, who has come to steal a top-secret invention that Krei is keeping in his office.
At the Lucky Cat Café, Aunt Cass is hard at work. She serves her customers cappuccinos with cute animal faces in the foam. Just Hiro arrives home from school, and receives a call from his friends, Aunt Cass realizes top celebrity chef, Bolton Gramercy, is in her Café. She tries to talk to him, but he speaks very rude to her in return and goes back to reading his paper. Meanwhile, Hiro and Baymax arrive at Keir Tech, where Krei is recovering from the toxin he consumed. The team learns from Krei that Momakase stole half of a prototype gravitational disruptor. The other half of the device is hidden in another safe in Krei's office. As the team inspects the office, finding a lot of stuff chopped up by Momakase, Hiro receives a call from his Aunt wondering where he is. He told her he was going upstairs to study, and she found his room empty with only Mochi under the bed sheets. Hiro tells her that he meant the upstairs school library, and he is having a study group with his friends. Cass is not convinced and believes that Hiro is out bot-fighting. So she goes out to find him, armed with her cooking knives.
Aunt Cass arrives in Good Luck Alley and finds a place where she believes the bot-fights are taking place. She walks up to the thugs guarding the entrance, who check her bag. When they find her knives inside, they think she is a fighter and escort her inside. Cass is then given an apron and ends up in the arena of an underground cooking competition called "Food Fight". Cass is, at first, not interested in entering, but when she meets her opponent, Bolton Gramercy, who insults her again, she decides to compete. Cass and Gramercy's challenge is to make the perfect crème brûlée using gummy iguanas, cilantro, and ostrich eggs. They have thirty minutes to cook and present their dishes to the judges. The two chefs race against the clock to make their crème brûlée. They both finish with seconds to spare, and present their dishes to the judges. Gramercy, however, ends up burning his. The judges taste both crème brûlée, and after some quiet consulting Cass is declared the winner. Since Gramercy lost, he has to give away his knives to Cass. Meanwhile, Momakase is visited by Yama, who hired her to steal the gravitational disruptor. He is not pleased that she only stole half of the device, only to be reminded that he hired her to steal what was in Krei's safe. However, she agrees to steal the other half on the account of extra payment.
Hiro and Baymax arrive home very late, after doing some investigation with the team. Hiro is worried about what to say to Aunt Cass, only to discover that she is not home. Suspecting she went out looking for him, Hiro and Baymax almost head back out to find Cass, but she walks through the door moments later. Hiro is the first to expresses how worried he was not knowing where she went. Cass says nothing about where she went and goes to bed. The next night, Momakase returns to Krei Tech to steal the other half of the gravitational disruptor. She sneaks into Krei's office where Hiro, Baymax and Wasabi are waiting for her. Momakase users her martial arts and swords skill to fight the three heroes. Using graphene bladed weapons that are thinner than paper but stronger than steel, she instantly slices through their armor and escapes with the other half of the device. Meanwhile, Cass starts sneaking out every night to go food fighting. She becomes quite a competitor, especially when other chefs try to pull off some deceitful stunt to make her lose. She always comes out victorious and claims the knives of her opponents. At the same time, she ends up oversleeping and keeps forgetting to open the Café on time. Pretty soon, Hiro starts to wonder where she keeps going every night. So, he and Baymax decide to follow her to Good Luck Alley and see what she is up to. Meanwhile, Momakase is visited by Yama again, pleased that she got the rest of the gravitational disruptor. He is just about to pay her, but Momakase has decided to sell the device on the black market to the highest bidder. She then poisons Yama with toxic sushi and has him sent home before heading down to challenge Cass.
Hiro and Baymax find Cass in the cooking arena, just as Momakase shows up. Hiro and Baymax are then thrown out, but call in the rest of the team. While Cass and Momakase are busy competing against one another to make sushi in record time, Big Hero 6 go upstairs to retrieve the gravitational disruptor which is under guard. Momakase tries everything to make Cass lose, but all her efforts backfire. She then notices a commotion going on in her office. Before heading upstairs to check it out, she finishes her dish and presents it to the judges. She also traps Cass in a net, so she cannot get her dish to judges before the time runs out. Big Hero 6 beat Momakase's men and retrieve the gravitational disruptor. However, Momakase shows up and engages the heroes in a fight. Wasabi has the gravitational disruptor and accidentally activates it when Momakase attacks him. Everyone at the fight ends up floating in zero gravity. Cass gets free and presents her dish to the judges with just a second to spare. She is declared the winner once again, much to Momakase's chagrin. She attacks Cass but gets caught in her own net just as Hiro deactivates the disruptor, restoring the gravity. Later, Momakase is arrested and the gravitational disruptor is returned to Krei. Chef Gramercy also apologizes to Cass for his behavior towards her, and she gives back his knives.
- The premiere date for this episode was scheduled for March 22, 2018, but Bob Schooley confirmed that this announcement was not the official US premiere date.
- This episode guest stars British chef Gordon Ramsay and food show presenter Alton Brown. Some of Ramsay's and Brown's appearance and mannerisms were incorporated into their characters of Bolton Gramercy and Yum LaBouché, respectively.
- The food fight competition itself is a parody of popular cooking television shows such as MasterChef or Hell's Kitchen.