Finn makes amends at the Candy Hospital while Jake tries to connect with their unexpected houseguest.
The episode opens the morning after "Two Swords", with a restless Finn on his bed, emitting a lengthy groan. His groan fades into a similar groan from "Grass Guy", who is seen lying on the grassy rooftop of the Tree Fort. Jake asks after Finn, who tells him that he feels "like crud". Jake asks if he feels that way because he lost his Finn sword, because he lost his arm again, or because he has a grass clone living on their roof, all of which which Finn responds "no" to. Finally, when Jake asks if it's because he had fatally injured Susan, Finn gets up immediately in panic, realising he had forgotten about her.
Before going to see Susan, Finn and Jake make a visit to "Grass Guy" on the rooftop, who is deep in contemplation. Finn informs him that he has to run an errand, but that Jake will stay behind at home. Finn tells an apprehensive Jake to pretend "Grass Guy" is him, correcting himself to say, "He is me." Jake concedes, and the first thing he does is make meat loaf for "Grass Guy", who expresses delight at the dish, calling it his favourite. He puts on Finn's meat loaf bib, an action which Jake is initially displeased by but quickly gets over. However, as "Grass Guy" attempts to eat the meat loaf, he realises that his grass body is incapable of digesting such foods. Jake tells him that they will find him a new favourite food.
At the Candy Kingdom hospital, Finn stands over Susan's bed where she is still lying unconscious. He apologises for not being able to save her earlier because he lost control of his arm, now understanding that that sense of uncontrollability must have been what she had felt too. He blames himself for her state.
All of a sudden, Doctor Princess bursts into the ward and begins reproaching Finn for causing Susan's injuries. She asks him what he will do to fix the situation, to which he says he will do anything. Upon hearing this, Doctor Princess removes her doctor's coat for Finn to put on. Declaring Finn a doctor, wishes him good luck and starts to leave. When Finn protests, she confesses that she was never a real medical doctor, but that she came for an X-ray and was mistaken for one because her first name is "Doctor". With that, she leaves. Mr. Fox comes up to Finn to ask for help, and Finn starts to say he is not a real doctor, but stops when he sees the fox crying.
Back at the Tree Fort, Jake digs up Finn's flute for "Grass Guy" to play. However, it turns out that "Grass Guy" does not breathe either, so he cannot play the flute. When he becomes frustrated by this, Jake quickly reassures him again. They then decide to go out and fight some evil, something that he will be sure to like. "Grass Guy" has a brief vision of a grassy hill, and says he knows somewhere evil they could go to.
At the hospital, Finn attends to Mr. Fox, who has a large painful splinter stuck in his paw. When Finn pulls it out with ease, Mr. Fox calls him a real healing genius, and Finn is visibly pleased by the compliment.
Jake and "Grass Guy" make their way into a grass maze, which Jake comments looks familiar. A few steps in, a grass monster emerges out of the maze wall and pins Jake onto the ground to attack him. "Grass Guy" immediately comes to his rescue with his grass sword, slicing the monster's head off. Jake tells him he did a great job, and "Grass Guy" is visibly pleased by the compliment.
Ice King visits the Candy Kingdom hospital, and Finn learns that his back is in constant agony. Finn attends to his back pains immediately by bending him in half. Ice King yells in pain, but quickly realises he feels much better and "500 years old again". Finn internally muses over how right being a doctor feels.
Back at the maze, "Grass Guy" slices the final monster dead before it can finish giving a riddle. Jake is wary, as "Grass Guy" has shown to be unnecessarily violent throughout the maze, but still tells him he did a great job. "Grass Guy" slices a door leading out of the maze, and the pair exit. They walk up a grassy hill, where the Grassy Wizard stands outside of his house berating them for trespassing. "Grass Guy" tells the wizard that he was made by him, and begins asking him questions about why he was made, wanting to know if he is bad, part of a conspiracy, one of Finn's enemies, or an eternal curse. The wizard laughs and reveals he simply thought it would be cool to make a grass blade. When he orders "Grass Guy" to chop up Jake for trespassing, believing "Grass Guy" will follow his orders since he is his "master", "Grass Guy" responds with violence by continuously punching the wizard. Jake finally lets "Grass Guy" know that it is not right to fight evil in such a way, and he becomes uncertain of his actions throughout the day.
In Susan's ward, Finn is about to drop a sword straight down to Susan's head to rouse her fighting reflexes and wake her up, when Doctor Princess returns. She quickly throws her sunglasses towards the sword, deflecting it before it can reach Susan. She tells Finn that is not the way to practise medicine. Mr. Fox returns as well, his paw now heavily infected after Finn's treatment. Ice King comes into the ward too, and his back pains prove to have been only temporarily alleviated when they act up again. Finn realises then that he is no doctor.
Finn leaves the Candy Kingdom, ruminating over his day. Being a doctor felt right for a while, but he realises the people he treated would have been better if he had just stayed out of it. He meets Jake and "Grass Guy" in the midst of his walk out, who have brought the Grassy Wizard to the Candy Kingdom for medical attention. As the wizard is wheeled away, Jake tells "Grass Guy" that he did the right thing in the end, just like Finn would have. However, "Grass Guy" does not feel vindicated. When Finn says, "Good job, grass me.", he replies, "But I'm not you. It's clear that I'm someone else." With that, he gives himself the name 'Fern'.
Fern takes Starchy's motorbike and rides off into the sunset. When Finn is about to stop him, Jake tells him to let him go. As Fern speeds away on the bike, he pulls off his hat to let his hair free, and red and yellow flowers can be seen glistening in his green-gold locks.
Back in Susan's ward, a blade from a ceiling fan breaks off and flies down in Susan's direction. A mere inch away from her face, she suddenly wakes up and catches the blade before it hits her.
- Doctor Princess
- Susan Strong
- Mr. Fox
- Ice King
- Grassy Wizard
- Grassy Monsters
- Assisstant Doctors
- Rattleballs (cameo)
- A large number of non-Candy People are seen in the Candy Kingdom, this is including but not limited to, Finn, Jake, Fern, Susan, Ice King, Mr. Fox, Doctor Princess, and The Grassy Wizard.
- Doctor Princess reveals that she does not have a medical degree (she came in for an x-ray exam) and that 'Doctor' is simply her first name. This means that 'Doctor Princess' is her legal name.
- Rattleballs got put back together after Susan broke him apart in "Reboot".
- The Grassy Wizard returns in this episode since his debut from "Blade of Grass."
- Finn's/Fern's favorite food being meatloaf is mentioned again. This was mentioned only in "Still" and "Jake Suit."
- The way Fern punches the Grassy Wizard (making his arm into a huge, spiky fist) is extremely similar to how Finn punches Martin with his spirit arm in "The Tower."