The episode starts off with Finn and Jake along with Lady Rainicorn and Lumpy Space Princess are running away from a group of Candy zombies. They rush to the castle entrance and close the door shut. Finn says "It’s happening again", referring to what happened in "Slumber Party Panic". They find Princess Bubblegum and she tells them that she once again is responsible for causing the zombie epidemic to strike the Land of Ooo. She explains to everyone how she was in the lab experimenting with a sample of Candy zombie flesh when Cinnamon Bun walked in telling her that he was hungry. She told him that she was busy, but while she wasn’t looking at him, he ate the Candy zombie flesh out of hunger, which made him turn into a Candy zombie. Princess Bubblegum said that she managed to escape, but could not stop the rest of Ooo from getting infected. She tells them that she still has all her notes for a cure she was working on. Finn and Jake along with the others are relieved, but the Candy zombies break one of the windows and bite Princess Bubblegum, turning her into a zombie. While she was being infected she tells Finn not to worry and tells him he still has her notes for the formula and to let “Science” do all the work. As she is half way from turning into a zombie she tells them “Science is-“and then she gets cut off as she is finally infected and starts moaning. Lumpy Space Princess then hits Princess Bubble gum with the hammer that she was holding earlier when she suggested to board the windows before the zombies broke in. Lumpy Space Princess quickly boards up the window, while fighting the zombies. Jake then appears with the notes and says that the notes don’t make sense and that they are all “Gobblygag”. Finn then tells them that they should each make their own version of the formula and that one of them is bound to get it right. They go in the lab and start making their formulas, while they are making them Finn and the others notice Princess Bubblegum’s lab rat moving around like its dancing and Jake says that’s neat and they continue working on their formulas. They finally finish making their formulas and quickly rush to the same window where the Candy zombies were trying to get in. Finn tries his formula first, but the zombie he tested it on starts to grow wings and infects the rest of the Candy zombies with the same formula that was in his body and they start to fly. As they are flying you can see Starchy, who is still not infected on top of a building he then says “Oh my that’s a lot of zombies down there” and is happy that he is safe up, but as soon as he says that he is quickly grabbed by one of the flying zombies. He is thrown into the window, breaking the wooden boards. Finn tells everyone to run up the stairs and they all go up to one of the watch towers and close the door. Finn tells Jake to use his and Lady Rainicorn’s formula, but is then interrupted by Lumpy Space Princess, who pushes them out of the way and says that her formula will cure the zombies because she made the “prettiest formula”. She opens the window and pours it on the zombies, which makes them have unusually large lips. She then is fascinated by the lips and she goes to lick the rest of her formula to get lips like the zombies. She runs down and starts licking what is left of the formula pushing all the Candy zombies out of her way and is excited that she is going to look “So freaking hot”. Then she quickly surrounded by the zombies and gets infected as well. Finn then quickly tells Jake to use the last formula that he and Lady Rainicorn made. Jake spills it on all the zombies hoping it will work, but with the same horrible results as the other antidotes. This time the zombies get giant muscles and quickly start soaring straight to the tower. Finn and Jake along with Lady Rainicorn all scream in horror and the zombies quickly smash part of the tower. Finn asks Jake where they should go next, Jake then says they can go barricade themselves in the lab. They rush in and Jake stretches his arms to quickly shut the door, while the zombies quickly start punching the door to get in. Finn quickly asks Jake if anyone got bit, Jake tells him that they are ok and that the door is made from candy steel. While Jake is saying that to Finn a Candy zombie comes out from one of the lockers next to the door, Finn screams and Jake quickly turns around to find the zombie right behind them. Jake quickly pushes the Candy zombie back into the locker and uses it along with a potted plant to barricade the door. Finn asks Jake if the Candy zombie got him, Jake tells him that he thinks he’s ok and that he only has a little bite. Then he quickly starts to get infected, as the infection is reaching his body Jake starts to stretch his arm to avoid being fully infected. Lady Rainicorn worried, calls out to Jake and he tells her “It’s all good sweetie I can stretch forever”, which is not true as seen in “The Limit”. Jake then whispers to Finn to hurry up with making the antidote as he cannot stay stretching too long. While Jake is running around stretching his arm Finn is trying to come up with how to make the antidote. Jake then suggests Finn should check one of the books next to Princess Bubblegum’s lab rat. Finn grabs one of the books and says that it has a glossary of symbols. Jake tells him that’s great while trying to not get infected. Finn then hears the lab rat tapping on the glass and says that the rat has serious dance fever. Jake starts to get exhausted from stretching too much and goes in the “Sciencey shower”. Lady Rainicorn is worried about Jake and comes to him, he quickly tells her not to get near him because he might get infected. The infection starts spreading faster and Jake starts stretching inside the shower. His body is soon wrapped of in his stretched arm and he is finally infected. Lady Rainicorn gets very scared for Jake. Finn tells her he will have the antidote soon and tells her that whatever she does to not let Jake out, because even though he looks likes the Jake that loved her he is just a zombie now. Lady Rainicorn doesn’t listen to Finn and opens the shower door to the now zombified Jake, who starts hugging and Kissing her, only to bite her getting Lady Rainicorn infected. Finn turns around while calling for Lady Rainicorn when he quickly screams from the two zombies and runs along with the lab cart he was using. He also grabs the rat along with its cage and puts it at the bottom of the cart. Soon the Candy zombies break into the lab and Finn is forced to run inside the shower to continue making the antidote. As he gets in he drops the book he was reading outside. The zombies start cracking the glass door of the shower and Finn is now very scared and worried. Finn then tells everyone that he is sorry saying their names in abbreviations except for Jake: “Sorry LSP, PB, Jake LR, PB, POOPOO, DOODOO”. He then tells the lab rat how its funny that he doesn’t even know it’s name, the rat then taps on the cage. He asks “what is it girl?” she taps her cage where there is a label that says “SCIENCE”, and then Finn realizes that the rat’s name is Science. He remembers what Princess Bubblegum was saying to him while she was being infected. He then lets Science out on the table and Science starts to read the notes and move things around, he then opens a little music box and pulls a jar that’s labeled “Knife juice”. Finn starts to follow what Science is doing pouring the Knife juice in the beaker and mixing in test tubes along with red powder, then pours a giant container of liquid in, which finally makes the antidote. The antidote changes color from blue to orange and is ready. Finn quickly runs up to where the zombies are and tests a small amount of the antidote on Jake with an eye dropper. Jake is quickly cured and tells Finn that he did it, but is quickly infected again. Finn looks at Science and Science nods not knowing what to do. The zombies start to get closer to Finn and have almost broken the shower door. Finn tells Science to not worry because he has a “disgusting idea”. Finn grabs the antidote and pours it all on his body and runs to the zombies that surround him. As they all start biting him he screams “Oh my glob!” then you see that Candy Kingdom is back to normal and the all the Candy people are cured. Everyone is apologizing for infecting each other, Princess Bubble gum then announces that the royal day of apologizing is over. Then comes up to give a medal of “Heroic bravery” to be Finn, she then says “Finn the human would you please move out of the way” and gives the medal to Science. She then tells all the citizens of Candy Kingdom to rejoice and the episode ends.