The episode begins a few days after where the previous one left off: Peridot is still holed up in the bathroom. She's still refusing to talk to the Gems. The Crystal Gems are still trying to get her to talk. And Steven is still the only one allowed in the bathroom because he actually needs to use it. They try to propose a trade, but the only thing Peridot is willing to trade for is her gear — which the Gems did away with. Peridot's hostile and insulting attitude is so annoying even calm Pearl gets irritated with her, but Garnet decides that if Peridot won't talk, they will have to investigate whatever "the Cluster" is on their own. So they leave, telling Steven he must remain behind to watch over Peridot. Garnet tells him she has one more thing to tell him.
- Garnet: [makes Heart Symbol with her hands] I love you! 'Bye!
Steven decides to make himself some soup once the Gems are gone. He invites Peridot to join him since she's in there partly because she hates the Crystal Gems and doesn't want to be in their presence. But even with them gone, she stubbornly refuses to come out.
It begins to rain shortly after her refusal, and when the thunder starts, Peridot flings herself out of the bathroom in a panic, certain that it's too late — the Cluster is emerging and it's the end of the world! Steven assures her it's just thunder, which happens when it rains sometimes. Peridot is confused and bewildered, clinging to Steven. He explains to her in a simplified way about the water cycle. She doesn't quite get the metaphor about the soup being the ocean and evaporating into steam clouds which become heavy and form rain.
- Peridot: So scalding liquid falls from the sky?!
Steven tries another way to show her rain is not harmful. He goes out and runs around in it, getting soaked and whooping cheerfully the whole time. Peridot watches him, torn between being wary and being confused. She ventures far enough out of the house to get her fingers wet, and even takes two whole steps out the door. Steven congratulates her about being brave enough to do so. Peridot, in turn, congratulates Steven on being more intelligent and knowledgeable than she thought he was. She decides that he is smart enough and has enough knowledge about the Earth that between the two of them they can do something about the Cluster... but they must go back to the Kindergarten, because without her limb enhancements, her fingers and screen, that's the only place she has a backup of her logs. Steven considers this and agrees, but insists she must hold his hand the entire time.
As they leave the warp pad to walk back to the platform to take them underground, Peridot remarks how badly maintained this Kindergarten is, and asks how Steven emerged. When he explains he didn't come from a Kindergarten but from his mom and dad, Peridot is confused.
- Steven: That's a story I like to call "The Ballad of Rose and Greg..."
Peridot brushes him off, disinterested. They reach a panel that needs power, but Peridot can't open it on her own. Steven is able to do so easily. Peridot can't reach the control panel. Steven crouches beneath her to lift her so she can get to it, telling her that it's okay to ask for help. Once she's got the control panel lowered to her current size, she shows Steven what the Cluster really is. It's like the gem mutant experiments, only much, much bigger. An amalgam of millions of gem shards, it slumbers inside the Earth, incubating. But when it emerges, it will be so immense that it will destroy the Earth! If they can't get off planet, Peridot reasons, her knowledge of the Cluster plus Steven's knowledge of the Earth combined should be enough to stop it.
Steven assures Peridot he doesn't really know that much about the Earth; he was only able to tell her the story about the water cycle because when he was small, he too was afraid of thunder and his dad told him so he wouldn't be afraid. Peridot still doesn't get it and allows that perhaps they'll have to ask "the dad" for help, but steadfastly refuses to consider talking to the Crystal Gems. Before Steven can try to persuade her again, a throng of gem mutants appear and attack.
Steven bubbles himself and Peridot, who panics and yells at Steven to do something. Steven tells her there's not much he can do besides this. As the mutants corner them, the Crystal Gems arrive and destroy the fusion monsters. The Gems begin to scold Steven for letting Peridot take him here, but Peridot stands up for him.
- Peridot: He did what he was told.
Then, swallowing her hostility and no small amount of her pride, she catches herself on being about to address Garnet, Amethyst and Pearl as "clods", backtracks, and refers to them as the Crystal Gems — and tells them she's ready to talk about the Cluster.
- Beneath the Earth: The Cluster lies within the Earth's core.
- The Blind Leading the Blind: When Steven explains to Peridot how rain and thunder work, she immediately assumes Steven is an expert on everything about Earth, so just the two of them should be enough to stop the Cluster. Steven knows better, and explains that he only knows a little more than her.
- But I Read a Book About It: Peridot got all her information on Earth and the fusion experiments from old reports she had stored on her arms.
- Peridot is still entrenched in Steven's bathroom at the start of the episode.
- When Pearl offers a trade for information on the Cluster, Peridot shoots back that she'll only trade for her limb enhancers, which Amethyst threw away in the previous episode.
- Peridot mentions her visit to the Kindergarten in "Keeping it Together", and reveals that she backed up all her files when she was there.
- Character Development: Peridot on seeing that Steven genuinely wants to help her but really cannot handle the Cluster with her— being Just a Kid and one "hybrid" against many forced fusions— realizes that she has to swallow her pride and ask the Gems for help, especially since they saved her and Steven.
- Compliment Backfire: Peridot tells Steven that he's smarter than she initially thought, though she seems to mean well by it.
- Crippling Overspecialization: Steven's Barrier Warrior status works against him here, as he can only defend against the fusion monsters, not retaliate against them.
- Didn't Think This Through: Steven tries to get himself and Peridot away from the gem mutants by running to a corner, but he's shocked to discover that they've cornered themselves.
- Double Meaning: Peridot steps out in the rain, and says "Cool." She's echoing Steven's slang, noting the temperature of the water, and unusually for her, learning about something by feeling it with her bare hands.
- Earth-Shattering Kaboom: If the Cluster emerges, this will be the result.
- Enemy Mine: The episode ends with Peridot agreeing to join forces with the Crystal Gems to stop the Cluster, after Steven convinces her that he isn't as omniscient as she assumed.
- Exact Words: Peridot invokes this when Garnet tries to call out Steven for taking Peridot with him to the Kindergarten, saying that he was Just Following Orders in "watching him."
- Exposition Cut: The episode ends with Peridot about to explain everything she just told Steven to the gems.
- Fear of Thunder: Peridot is unwilling to leave the bathroom even after the Gems have left. When she hears the thunder, though, she runs out of the bathroom under the belief that it signals The Cluster hatching.Peridot: IT'S HAPPENING!
- Fish out of Water: Without the touchscreen computer her artificial arms had, which contained both her logs and any Gem records she had, Peridot has no source of information on Earth save for Steven, which means that she's caught off guard by things like thunder and rain.
- Freak Out: The thunder rattles Peridot enough that she runs out of the bathroom and into the opposing wall.
- Harmless Villain: Pearl points out how harmless Peridot currently is without her limb enhancers, which prompts a defensive outburst from the shorter Gem.
- Holding Hands: Steven makes Peridot hold hands as they investigate the Cluster, nominally so they'll stay together, but more likely Steven's idea of a bonding activity. Peridot takes him entirely seriously, and only lets go after politely pointing out when she needs both hands.
- How Is That Even Possible?: When Peridot's learns Steven is a Half-Human Hybrid, she asks how that's possible. After he refers to the tale as "The Ballad of Greg and Rose", she stops caring.
- I'm Standing Right Here: Pearl speaks of Peridot even as they're on opposite sides of a regular door.Pearl: Don't worry, she's harmless without her limb enhancers.
Peridot: I'M NOT HARMLESS!
Pearl: Oh, hush up!
- Internal Reveal: Steven reveals his hybrid nature to Peridot (she having previously assumed him to be a full Gem Quartz of some kind and a product of the Kindergarten), though she doesn't pursue it further, and may not have fully grasped the significance.
- Locked in the Bathroom: Peridot starts the episode in Steven's bathroom. Though she initially refuses to leave once the other Gems head out, she bursts out when she hears the thunder.
- Locked Out of the Loop: Peridot's lack of reaction to Rose's name and her non-mention of the fallen Crystal Gems used in the experiments imply that her superiors on Homeworld have kept her in the dark about all the details of what went down on Earth.
- Mistaken for Apocalypse: Peridot apparently mistakes the sound of the thunder for the Cluster awakening.
- Nice Job Breaking It, Hero!: Amethyst tossing Peridot's limb enhancers into the sea makes it harder for the Crystal Gems to negotiate with Peridot.
- Not So Different: Steven reveals to Peridot that he used to be scared of thunder as well, until his dad explained to him about the water cycle. They would've had a bonding moment after this.
- Oh Wait!: Pearl attempts to negotiate with Peridot, proposing some kind of trade. Peridot says "Oh sure! Why don't you just give me back my leg enhancements and my arm attatchments with my screen and my log and all my information? Oh wait! You destroyed them! So no, I don't think we can reach some sort of agreement!"
- Pet the Dog: After Steven explains and shows Peridot rain, she goes out of the way (and clearly goes against the behavior she's used to) to say "Thank you."
- Rage Quit: The Cluster basically amounts to this: when the Homeworld realized they were going to lose, they planted it to destroy the entire planet.
- Redemption in the Rain: Peridot becomes openly willing to cooperate with Steven, and even starts empathizing with him, when he brings her out into the rain, with choir music and a softer, slower version of her leitmotif in the background.
- The Reveal: The Homeworld left Earth alone to use it for their experiments, using the Kindergarten to grow Gem shards to use in fusion mutants, including the Cluster, which is made of millions of them.
- Reveal Shot: The episode begins with the Crystal Gems and Peridot arguing from opposite sides of the bathroom door, with Steven apparently absent. Then a flushing toilet is heard, Steven walks in from the bathroom side, and he tells Peridot she doesn't have to look away anymore.
- Sidetracked by the Analogy: When using his soup pot as a metaphor for rain, Peridot takes it too literally and assumes rainwater is scalding hot.
- Smarter Than You Look: Basically what Peridot says of Steven after he explains rain to her.
- Suppressed History: There are some hints that the reports Peridot read glossed over some details. For example, she doesn't mention the use of fallen Crystal Gems in the fusion experiments at all. Neither does she realize the significance of Steven's gem, despite recognizing it as some type of quartz and Steven calling his birth "The Ballad of Rose and Greg." She regards the reason Homeworld left Earth was because it ceased being a viable colony, not because of a civil war that broke out and forced them to leave. Not that it's entirely false though.
- Teeth-Clenched Teamwork: You can tell Peridot isn't thrilled about working with the Crystal Gems. However, she's far more open to Steven's assistance.
- Title Drop:Steven: Everything is fine. It's just thunder. It happens when it rains.
- Ungrateful Bastard: Subverted; Peridot opens up to the Gems after they rescue her and Steven in the Kindergarten. She even makes an effort to not call them "clods".
- Universal Universe Time: While telling Steven about the Cluster, Peridot mentions that she learned about the Cluster by reading "a few hundred years worth of reports". This makes it seem like the Gem Homeworld and its empire are inexplicably using the same units to measure time as on Earth. Although she could have been using a different definition of "year", perhaps defined based on how long Homeworld takes to orbit its own star, it seems more likely that she speaks in terms of years simply for the same reason that she can easily communicate with Steven in the first place.
- Verbal Backspace: Peridot starts to call the Crystal Gems "clods" again, only to catch herself and use the proper title.
- Wham Episode: The Cluster is revealed to be an artificial fusion made of millions of Gem shards located in the Earth's core, and Peridot decides to work with the Gems to stop the cluster.
- What the Hell, Hero?: Subverted; Garnet starts to call out Steven for taking Peridot to the Kindergarten, but Peridot explains he was following Exact Words and trying to help her with the Cluster. She then agrees to tell the Gems about what they're facing.