The Face of Evil is an Adventure Time episode that involves Finn and Jake finding Lemongarb's face in their house.
Finn and Jake find Lemongrab's face in their house and they must go to the Nightosphere to return it to his body.
Finn and Jake are going to sleep when they hear some strange grunting noises. They search the tree dome to check for where it's coming from and they track it down to a trunk in their house. They open it and in there they find Lemongrab's face lying in the trunk screaming. Finn picks him up and asks him what is going on. Lemongrab tells him about how his brother was possessed by creatures from the Nightosphere and he attacked him and took away his body and left behind his face in Finn and Jake's trunk for some reason.
Finn and Jake do the whole putting milk on a Phil face thing to go into the Nightosphere, carrying Lemongrab's face in a basket along with them. Lemongrab tells them that his body and Lemongrab 2 are in the black castle of evil where the king if the Nightosphere is. He knows this because he has the ability to sense where his brother is. Finn and Jake get spotted by some demons who try to destroy them because they are mortals who are not allowed into the Nightosphere so they fly across a bottomless pit toward the castle being chased by them and get the other side to have no better of a time when more demons and creatures attack. Finn and Jake hurry off and hide in a cavern finally losing them.
Finn is worried about returning Lemongrab's face to his body thinking that they won't survive because they barely even survived the first part. Then they remember how they disguised themselves as demons that last time they went into the Nightosphere. Jake morphs into a demon shape and Finn sharpens the ears on his hat to look like horns and puts on scary red glasses. They go out of the cave and get more respect and head for the castle. They start to hike up the mountain and go to the castle but then they find a line of demons and one tells them that they have to stay in line and can't cut. All of them are waiting in line to get the king to accept their return to the surface again.
Finn and Jake try to find an alternative to get up there without having to put up with the line. So they crawl around the mountain the hard way and have go go through a lot of trouble with twists and turns and demon attacks. Lemongrab tells them about how they can use his face to put on the face of another demon and he will have control over it. Finn and Jake do that and it is a great help. They can also remove the face of Lemongrab from the demon to kill the demon itself and get things over with faster.
When Finn and Jake are almost to the castle, they get caught by the demons who saw them in the first place who could see through their disguises and knew they were the importers. Conveniently, they are supposed to take them to the king of the Nightosphere so they can turn them in. Finn thinks of how he could have just done that the whole time. When they go to the Nightosphere, They see a dark shadowy figure there that the demons are treating like the King. Strangely his voice sounds nothing like Hudson's. The figure comes outward and it turns out to be a possessed Lemongrab 2 and the body of Lemongrab 1 with his face replaced by Uka Ukawhich leaves a mind-boggling question of where is the real Hudson Abadeer and what happened to him?
Lemongrab 2 is angry at them for having come so close to returning the face of Lemongrab and wants them coming out no further. He sends out the most powerful of demon troops to attack them and end them forever. Finn uses his demon sword on them but because of the demonicness of all of them they only get stronger and more powerful. Finn didn't bring along any other swords and neither did Jake. They try to use Lemongrab's face on one of them but it is no use. Demons are surrounding them all over and there is no escape. When Finn thinks it is all over for them, he sees a the shocking sight of Flame Princess, Metal Overlord, Barry and Bones just simply standing there informs of the demons looking and smiling at him calmly.
Paralyzed in shock, Finn asks why she's there hoping it's not because she really is evil. Flame Princess tells him that it's not because of her being evil at all but because fans were unhappy with the way she hadn't been appearing much in the show lately which only confuses Finn more with the fact that they are not in a show. Flame Princess tells him that they are in a cartoon called Adventure Time but Finn keeps denying it thinking that he is actually a real human being.
Suddenly Hudson Abadeer is seen floating out from behind the seats where the Lemongrab's are sitting to explain what's going on. In the background, his daughter Marceline and her boyfriend Ash are seen in cages hanging for some strange reason. He tries to convince Finn that they really are in a cartoon and makes tons of strange and crazy things happen. Such as Ice King and Flame King playing cars on a floating rock platform. Ice King gets mad at Flame King and shoots out a blizzard at him blowing him away. A baby Finn is seen doing the tough tootin' baby dance. Then Lord Monochromicorn comes out of nowhere with Fionna and Cake riding on him. Lord Monochromicorn says something in morse code and Cake translates it to that he's pregnant. Lord Monochromicorn appears to be pregnant and pukes up gender swaps of Jake and Lady's Rainicorn Dog kids.
Random things happen everywhere and Finn still denies that he is in a TV show. He walks around in a world of randomness explaining his thoughts on the whole situation. He comes to the conclusion that he the strange occurrences are not because he is in a TV show, but because he is having a dream. He wakes up in his bed and Finn and Jake being woken up was just a dream that he woke up from. Jake wakes up too and tells Finn that he had the same dream. Now they are safe and the horror is over. Jake jokingly morphs his face into Lemongrab's face. Finn tells him to stop joking around and Jake stops and goes downstairs to make some bacon pancakes. He hears Jake making more Lemongrab sounds and sees his shadow over him and he tells him to seriously stop. Jake sticks his head out of the passage to the other room proving that that is not him. Finn turns around to see that that is really one of the Unstoppable demons with Lemongrab's face attached and baby Finn is riding him and is possessed by the same creature who possessed Lemongrab 2. Finn screams his scream from Burning Low and the screen goes black ending off the episode. THE END.