The episode begins with Finn, Jake, Lady Rainicorn, and Lumpy Space Princess running from Candy Zombies and just barely escaping to the Castle in the Candy Kingdom. They see Princess Bubblegum, and are informed that while she was experimenting with candy zombie tissue, Cinnamon Bun ate it out of hunger and then infected the entire Candy Kingdom while Princess Bubblegum escaped.
Princess Bubblegum then says that she is coming up with a cure, but a candy zombie bursts through the window and bites her on the shoulder. She tells Finn to use Science but, before she can explain, she is dragged out of the window and is turned into a zombie. All she could manage to say was: "Science is... MUHRAAHH!" Lumpy Space Princess then pushes Finn away from the window and, much to Finn's horror, hits zombie Princess Bubblegum with a board and nails the board to the window. Finn then says they will have to make their own formulas to cure her and the Candy Kingdom. Finn tests his cure on a candy zombie but with horrible results. The candy zombie grows wings and infects the other zombies with the same liquid giving them wings as well.
There is a view of Starchie on top of a building stating that he is glad he is not down there with all the zombies and starts to do a little dance, but is grabbed by Pineapple Guy and thrown into the window and breaks through the wood.
Finn and the rest of the group escape to the top of the castle to continue to try and cure the zombies. Lumpy Space Princess then drops her formula on to some of the zombies, but it does nothing but give them enlarged lips. Lumpy Space Princess wants this to happen to her, goes outside to lick it up, and ends up getting turned into a zombie herself. Jake and Lady Rainicorn then test their formula, but it only makes the zombies stronger. The candy zombies use their new abilities to reach the top of the castle and attempt to bite the group, so they retreat to the lab. The zombie Mr. Candy Cane comes out from hiding in the lab and bites Jake, who uses his Stretchy Powers to prolong the effects. However, Jake realizes he will become a zombie, so he goes into a sealed science shower. Lady Rainicorn feels sorry for him, and lets Jake out, only to be bitten. Then, the candy zombies break through to the lab, and Finn locks himself in the science shower. He then realizes that Science is Princess Bubblegum's rat. Science creates the antidote and Finn tests it on Jake, discovering that it works, but then Jake gets attacked by the mob of Candy zombies that were standing by him. Finn covers himself with the antidote, and the crowd of zombies break into the science shower.
It cuts to the Royal Day of Apologizing the next day. All the candy people are back to normal, and we see Princess Bubblegum awarding Science with a medal. It ends with Princess Bubblegum yelling rejoice three times to the cheering Candy People.
|Hynden Walch||Princess Bubblegum|
|Niki Yang||Lady Rainicorn|
|Pendleton Ward|| Lumpy Space Princess|
|Tom Kenny|| Starchie|
Candy Cane Guy
|Dee Bradley Baker|| Cinnamon Bun|