The episode starts off inside an underground sand city. Jake starts groaning and complains about feeling sick after he ate the candy in Finn's bag, but Finn claims that he did not bring any candy. Jake says that that must be the reason why it tasted different. He then asks what is going on with the spoon and Marceline so Finn looks at the spoon on top of a column where an invisible Marceline takes the spoon and taps it on a sand soldier that collapses. Marceline hands the spoon to Finn when Jake suddenly belches, echoing through the cave and causing some structures to crumble. Jake says that he feels better now and is hungry again, so he wants to go home. Finn states that they must give the spoon to Princess Bubblegum first.
Marceline begins to ask why Princess Bubblegum wants the spoon. Jake says that it is sometimes better not to know and Marceline agrees. Jake suddenly stepped in quicksand and starts sinking. Jake tries to get out several times but he keeps falling back in. Finn tells him to quit messing around, so Jake then grabs the support beam on the platform Finn and Marceline are standing on, causing it to collapse. Wondering if the entire place is made of quicksand, Jake asks for help in pulling himself out of the quicksand. Finn and Marceline grab Jake and pull and end up tickling him in the process, so Jake suggests that he should try something else and turns his body into a large corkscrew. As Jake starts drilling his body out, the city now begins to rumble and a large pillar of sand collapses causing an avalanche of sand. Jake manages to free himself from the quicksand and Marceline grabs them both before the sand avalanche hits them.
Marceline says that Jake demolished half the city with Finn adding that he sealed their only exit. Jake apologizes and says that he will dig their way out of there, but Finn and Marceline state that he will bury them alive/undead. Finn pulls out his Holo-pendant and calls PB for help, but their signal gets cut. Marceline asks if they have any more bright ideas and Jake states "snacks," which he simply suggests because he is hungry. Marceline says that she is hungry too and tells Finn to bust out the snacks. As Jake grabs a cookie to eat, Marceline asks where her red erasers are and Jake suddenly realizes that what he ate a while ago were the erasers. Marceline becomes enraged, but Finn tries to calm her down and that he will search for something red in the cave while they save their energy. While Finn tells Jake to be cool as he leaves, Jake asks Marceline how hungry she is. Marceline replies with a hiss and a frightened Jake apologizes, quickly saying "Please don't eat my blood!" Marceline tells Jake that she does not want to hurt him, but lets him know that things go crazy when she is hungry where she goes into a "feral mode." Jake simply whimpers in response. Marceline suggests that they tie her up, not that it would stop her from draining his blood, but so that he would not be scared.
Finn is walking beside some streams of lava saying that even Marceline's face would melt off if she tried to eat the lava. The scene cuts back to Marceline and Jake. Marceline is all tied up and getting worse and tells Jake to get her a bucket of lava. Jake denies her request and whispers, "Why did you leave me here, dude?"
Finn finds a blocked entrance with some red light shining behind it. He kicks the sand wall and it collapses, discovering that the people in the cave are not actually sand people, but people turned into sand by the red light. He passes by the corpse aiming the light and crawls into a hole. Switching back to Marceline and Jake, she starts to threaten Jake saying that she can smell his insides. Jake screams and the scene goes back to Finn.
Finn is still crawling in the hole. At the end of the hole, he finds a turtle-like creature shining the red light into a gem. The creature asks if that is Paris, but Finn tells him that Paris has been dead "for like 500 years." Finn asks what they were doing and the creature explains that they planned to reanimate the sand people to conquer its homeland at the center of the Earth. Finn then asks if he can have the ruby, but the creature says that it is an emerald. Insisting that it is a ruby, Finn says that he would like to take it. The creature gives it to him and walks into the shadows as Finn attempts to move the gem.
Jake has now covered Marceline up to her neck with sand as Marceline says that she cannot control herself much longer, apologizing before laughing evilly. Jake quickly tries to think of a plan, but is too hungry to do so. He then realizes that he could cook and eat Marceline before she eats him. After surrounding Marceline with lava, Jake spots Finn arriving with the gem. Jake says that it is not a ruby and that it is an emerald, but Finn denies it. Jake tells Finn that he may be a little colorblind and the gem is shown to indeed be an emerald. Finn suddenly notices that Marceline is gone, making Jake panic and attempt to run with Finn, but Marceline is overhead ready to attack. Suddenly, a giant worm bursts through the ceiling and Princess Bubblegum arrives, controlling the worm inside its mouth through tubes attached to her head. Jake tries to warn her that Marceline has gone rabid, but Marceline grabs PB and bites and drains her. Marceline returns to normal and thanks PB, saying that should hold her over till they get home. Finn asks if PB is okay, who then asks for the Spoon of Prosperity they found earlier. Placing it on her nose, she turns back to normal. The worm then leaps upward as the city is filled with lava, and the episode ends.
- It is revealed in this episode that Finn has a mild case of color-blindness, since he described seeing the emerald in a grayish-red shade.
- Princess Bubblegum refers to the Candy Kingdom as an "eternal empire."
- In this episode, Jake can be seen with toes on his feet as opposed to him not having any toes on his feet, since the animators don't draw them on.
- In the underground sand city one can see the emblem for the Triforce and the Medallion of Spirit (the symbol of the sand temple) from the popular Legend of Zelda franchise.
- The Underground City the friends explore at the beginning of the episode bears a little resemblance to the ancient Ruins of Montezuma, located near Camp Verde, Arizona in the United States.
- The title is a parody of the phrase "Red Scare" which denotes the promotion of fear of a potential rise of communism.
- In this episode, Jake says "This Little Piggy stayed home, and so should have I," while touching his foot which is a reference to the nursery rhyme "This Little Piggy."
- The worms featured in "Dentist" and "Red Starved" resemble the Sarlacc from "Star Wars: Episode VI - Return of the Jedi" (1983), the "Shai-Hulud" from "Dune" (1984) , the "Graboids" from "Tremors" (1990), the "Carnictis" from "King Kong" (2005) and the "Were-Worms" from "The Hobbit: The Battle of the Five Armies" (2014).
- The holo-pendant necklace Finn used in "The Other Tarts" and "The Great Bird Man" returns.
- Jake's fear of Marceline from "Evicted!" and "Henchman" returns once again.
- In the episode "What Was Missing," Marceline mentions wanting to drink the red from Princess Bubblegum's face, suggesting that pink is considered red enough for her to consume. This episode proves that she was telling the truth.
- When Marceline is "rabid" she is shown without shoes, however just after sucking out PB's color, she has her shoes back on in the next scene.
- This may not be an error as Marceline's clothes have been known to disappear whilst shapeshifting into other forms.
- The title card for the episode was designed by Derek Ballard, who storyboarded "Breezy" and "Nemesis" with Jesse Moynihan, both of which aired in season six.
- Princess Bubblegum's use of the Spoon of Prosperity emphasizes her desire to live forever, as shown in episodes such as "Goliad" and "The Vault," and her interest in the affairs of her kingdom.
- This episode shows that when Marceline bites someone, they do not become a vampire or a zombie. This is most likely due to the fact that she isn't actively trying to do such a thing when she drinks Princess Bubblegum's blood, but she has stated that she is capable of turning someone into a zombie by biting them in "Evicted!"