Marceline first leads a horribly conflicted Finn to an elderly musician's house, and forces him to hold the old man down so that she can feed. When Finn finally does so, she initially appears to bite the man's throat, but actually sucks the red out of his huge bow tie, leaving it white which it turns out he prefers.
They then go to a graveyard, where Marceline raises a skeleton army and leads it on a castle. When Finn goes ahead to warn the occupants, it turns out to belong to the Duke of Nuts, who is celebrating his son's first birthday. The Duke is horrified to hear of the approaching army, but when Marceline arrives she turns out to have been invited as the party entertainment. She starts playing a funky bass, and all the nuts and skeletons start grooving.
Behind the castle, Marceline orders Finn to kill a cute potted dimple plant. When he hesitates, the plant suddenly turns into a huge monster and tries to eat him.
The following morning, Finn and Marceline are walking in a berry field. He has realised that Marceline isn't actually evil and set the whole thing up to play with his mind. Suddenly Marceline is attacked by Jake, who is disguised as a giant strawberry. He tears her parasol away, causing the sun to burn her. Finn fights him, trying to explain that Marceline isn't evil, but Jake stakes her and she dissipates into black mist. Jake runs away celebrating, and Marceline emerges from Finn's rucksack in bat form. Finn thanks her for letting Jake overcome his fear of her, and she flies away.
Tropes
- Chronic Hero Syndrome: Marcy exploits it to trick Finn into being her henchman.
- Cute Is Evil: Marceline tasks Finn with slaying a cute little Dimple Plant. When Finn hesitates, the plant quickly grows into a giant monster and tries to eat him.
- Dark Is Not Evil: The episode plays with the notion of whether Marcy is or isn't evil. Ultimately, it lands on, no, she isn't. She just likes messing with people's heads.
- Dem Bones: Marceline raises a skeleton army and leads it on the Duke of Nuts' castle... as entertainment for his party.
- Face–Heel Turn: Subverted. Finn is forced to serve as Marceline's thrall, but it turns out she's just messing with him by pretending to do evil things.
- Faking the Dead: Finn and Marceline conspire to make Jake think he slew Marceline and saved Finn from her evil thrall.
- Foreshadowing: Marceline's ancient henchman suddenly becomes very spry when she frees him, since he was not actually suffering but helping her set up her joke on Finn.
- Good All Along: Marceline wasn't threatening an old man to force Finn into being an evil minion. The two of them were pulling a prank on him.
- It Amused Me: Marcy is in full troll mode here.
- Minion with an F in Evil: Seriously examined, with Finn's plight.
- Swallowed Whole: Finn, by the man-eating plant.
- Troll: Marceline goes around and does nice things but pins them under an evil guise to mess with Finn. She acts as if she's going to kill a guy when she just drinks the red out of his bow tie leaving him with a more-favored white bow tie, claims she's going to sack the Duke of Nuts' castle when she's really just there to play for his son's second birthday and tells Finn to kill an adorable Dimple plant without mentioning how it turns into an evil man-eating plant. By the time she suggests killing some pixies, Finn accepts wholeheartedly knowing that she's just trying to trick him into feeling bad before doing something good.
