"The Vault" is the thirty-fourth episode in the fifth season of Adventure Time. It is the one hundred and thirty-eighth episode overall.
When Finn starts sleepwalking and dreaming about the green Ghost Lady he filed away in his memory vault at the end of "The Creeps," Jake and BMO help him tap into his repressed memories to uncover a secret past.
This episode begins with Finn in the kitchen late at night making a midnight snack, although the bowl he has is empty. Suddenly, Ghost Lady emerges from the floor and begins trying to grab onto him. Finn starts screaming as Jake and BMO wake up to check on him, to discover that he was only having a nightmare. Jake and BMO are not happy with Finn's recurring nightmares about the Ghost Lady, and try to think of a solution.
Jake tells Finn that in order to solve this problem, he must visit his "vault" and find out who the scary lady is, Finn remembers the vault as the place where he stores all the memories he can't handle, and Jake is not amused to find Finn does that consciously. Jake presses for Finn to go into his vault but Finn rather aggressively refuses. Later, Jake comes to Finn claiming BMO has a new game. But when he turns it on, it is actually a hypnosis that makes Finn enter his subconscious to visit his "vault" of repressed memories.
As Finn goes into his hypnotic state, he explains to Jake his past lives; which included a comet, a butterfly, a "thing," and the Ghost Lady herself. He then views the Ghost Lady's life, where her name is revealed to be Shoko, a one-armed common thief who steals items for "clients" in exchange for money. The scene continues with Shoko and her pet tiger accepting a job from the Bath Boy Gang leader to steal Princess Bubblegum's amulet.
Shoko prepares to leave, but the Bath Boy Gang leader stops her to tell her that if she fails to retrieve the amulet, she will be killed. Shoko sneaks into Princess Bubblegum's castle by knocking herself unconscious and saying it was by the Bath Boy Gang. Princess Bubblegum "rescues" Shoko, brings her inside the kingdom, and treats her wounds. Shoko tells the story of her childhood to Princess Bubblegum, where her parents sold her right arm for a computer before abandoning her at a dojo. Princess Bubblegum is shocked and explains that parents are supposed to protect their children. Shoko takes Princess Bubblegum's words to heart, and the two form a friendship. Shoko considers staying with Princess Bubblegum and adopting a normal life, but a spy from the Bath Boy Gang threatens to tell the Bath Boy Gang leader that she abandoned the job, which would result in her death. Fearing for her life, Shoko "pretends" to beat up the spy, resulting in high praise of her combat ability from Princess Bubblegum.
Princess Bubblegum then requests Shoko's help on creating the first Gumball Guardians. Once the Gumball Guardians are created, Princess Bubblegum tells Shoko she has a surprise for her, ordering young Peppermint Butler to bring out a wooden box. Shoko opens the box to find a mechanical arm to replace the one her parents sold. Shoko starts to tear up and makes the excuse that she has to go back to her room.
Shoko places the mechanical arm on her right stub and cries as she remembers the threat that the Bath Boy Gang leader told her before she left that she would be killed if she didn't capture and return the amulet. The scene cuts to Princess Bubblegum sleeping, before a Gumball Guardian asks loudly if Princess Bubblegum is in danger. Princess Bubblegum tells him that she is fine and to go watch over the other Candy citizens. Once the Gumball Guardian is gone, Shoko sneaks into Princess Bubblegum's room and reaches for her amulet. However, the Gumball Guardian catches her in the act, setting off an alarm and waking up Princess Bubblegum. Shoko panics and swipes the amulet off of Princess Bubblegum's neck and jumps onto a platform below. However, Shoko is blasted by the Gumball Guardians' laser eyes, causing her to fall into a river of green, toxic chemical waste below her. Princess Bubblegum orders the Gumball Guardians to rescue her, but when one of the Gumball Guardians places his hand into the toxic waste, it is burned off. Princess Bubblegum tells the Gumball Guardians to take a break for the night as she looks on in sorrow. Shoko's pet tiger looks on from below, waiting at the riverbank. Bubblegum watches on for a few more moments before turning her back on the toxic waste river. BMO flashes "end of session" before turning off with a loud beep, waking up Finn from his hypnotic state before saying that the "past must be reckoned with."
He proceeds to call Princess Bubblegum, requesting her to come over right away. The scene cuts back to when Shoko fell into the toxic waste. The pool ripples and a mutated Shoko, who now appears the same as the scary lady from Finn's dream, crawls out of the waste. She crawls out to the fields bordering the Candy Kingdom to a tiny tree sapling, remarking that she now has two arms from her transformation. She then dies at the base of the tree as the sun rises over her. She is left at the base of the tree, only to let the tree grow around her, as she soon ends up in the floorboards of Finn and Jake's tree house.
The scene cuts back to Finn's tree house and Princess Bubblegum has arrived. Finn leads Princess Bubblegum to the kitchen, where he proceeds to knock over his oven and tear up a bunch of floorboards, surprising and confusing Bubblegum. Once Finn is finished tearing up the planks, it reveals a hollowed out hole where Shoko is buried. Shoko's ghost rises from the hole and hands Finn the long lost amulet before disappearing, showing her skeleton remains. This reveals that the Ghost Lady was only "haunting" Finn in hopes he would soon return Princess Bubblegum's amulet. Finn hands Princess Bubblegum the amulet where she exclaims in shock. She looks past Finn and sees Shoko's skeleton, realizing who the skeleton belongs to. Finn cuts her off from saying anything by stating that he is Shoko and states that Princess Bubblegum is not 19 but rather a "bazillion years old." Princess Bubblegum laughs nervously and Finn looks back at the hollowed out hole where a normal Shoko gives him the thumbs up. Finn comments that his vault feels lighter.
- The part where the Bath Boy Gang leader explicitly threatens Shoko by moving his finger across his neck and saying "Pretend my finger's a knife" was censored in some countries.
- Finn's sleeping suit looks different in this episode. It goes all the way up to his head and has the two bumps on it like his hat.
- In this episode the early construction of the Candy Kingdom is seen, as well as the creation of the Candy People, and the Gumball Guardians.
- The radioactive waste in the Candy Kingdom most likely originated from the Mushroom War.
- The tree Shoko dies under later grows into the tree that the Tree Fort is built upon, her radioactive body perhaps acting as a fertilizer to make it grow as big as it is in the present.
- In the past the Ice Kingdom Mountains are made of rock like regular mountains as seen from behind and to the left of the tree Shoko dies under.
- The promo art depicts Shoko's mother trading Shoko's arm for the laptop, as stated in the episode and it seems she is giving the arm to someone dressed liked Ash.
- Apparently, Princess Bubblegum's telephone number is composed of 5 numbers and, according to the order that Finn pressed them, her telephone number is "17441."
- Both Shoko and Finn were abandoned by their parents when they were little.
- It is revealed that Finn's past lives were a catalyst comet, a butterfly, a glowing pink blob, and Shoko.
- The game (entitled "Regression Simulator") that Jake loads on BMO to trigger the Vault opening is the first level of the indie game Super Hexagon.
- The outfit Princess Bubblegum wore is similar to outfits the Japanese wore in their farming era. "Shoko" is a Japanese name. The bath boys' lair is reminiscent of Japanese bath houses.
- Shoko riding a white tiger may be a reference to Princess Mononoke in which the main character, San, rode a white wolf to battle.
- While it appears that Bubblegum answers her phone with a thick German accent, she is actually speaking German as she says "hallo, Princess Bubblegum hier."
- The episode title refers to "The Creeps," when Finn first experiences the "Ghost Lady" and places his memory of the incident in "The Vault" of his mind.
- In the flashback showing Finn's former lives, he is shown as once being:
- The robotic arm that Princess Bubblegum gives to Shoko is similar to that worn by Finn's alternative selves in the episodes "King Worm," "Finn the Human," "Jake the Dog," and "Puhoy."
- During the past sequence, Mr. Cream Puff is confirmed to have been Bubblegum's boyfriend, as she reveals in "Slumber Party Panic" when trying to revive him from the dead.
- The Bath Boy Gang base is the haunted house as seen in "The Creeps." This explains why Finn had a vision of her haunting it in the episode.
- The hideout of the Bath Boy Gang is similar to the hideout of the Destiny Gang in the Farmworld universe.
- This is the third episode in which Princess Bubblegum is heard to speak German, after "What Have You Done?" and "Frost & Fire."
- Shoko's skeletal remains have remains of black hair, despite her having long, bright green hair as a result of her mutation, moments before her death. However, this could simply be the radioactivity wearing off.
- Although Shoko was mutated in the Radioactive river, her skeleton was still intact and must not have been affected.
- At the end of the episode, Shoko recovered her arm due to the radioactive river. This is a foreshadowing of Finn recovering his own arm later in the episode "Breezy."