In a flashback, King Edmund of the Dark Kingdom orders his subjects to evacuate. One of his handmaidens retreats into a room, where the cries of a newborn baby is heard.
In the present, Rapunzel and the group finally make it to the Dark Kingdom. While initially unsure, Cassandra and Eugene reassure her that they are behind her one hundred percent, and will be with her every step of the way. Meanwhile, Eugene talks to Maximus about the prophecy Demanitus predicted earlier about someone in the group betraying Rapunzel. Eugene makes Max swear to keep it between the two of them, but Pascal snatches the note from him, and gives it to Rapunzel.
The two of them talk about it, but Rapunzel is unable to believe that Cassandra would turn on her after everything they have been through. Eugene, however, is more worrisome, and wants to keep more of an eye on her just in case.
The group makes their way to old, forgotten gondolas. Cassandra volunteers to climb across the rope and restart the gondola that will ferry them to the center of the kingdom. Initially, Rapunzel and Eugene are wary that Cassandra will leave them stranded, but she succeeds in bringing the gondola back. The group travels across a deep chasm, where they are suddenly attacked by a mysterious man in a bear mask. They engage the man in battle, but he overpowers them. Adira shows up and not even she is able to defeat the warrior, who throws both her and her sword off the gondola and into the chasm below. As the gondola near the end of the chasm, Eugene and the man wrestle, which results in them falling into the chasm, as Rapunzel can only watch in shock.
Luckily, both him and the man are alive, having fallen on a rock ledge. The man prepares to strike down Eugene, but notices his eyes and stands down. Taking off the mask, he is revealed to be King Edmund, who is alive and well. The reason he will not fight Eugene is because the former thief is his son. Eugene is shocked by this and Edmund takes him to the castle.
Meanwhile, Adira is fine as well, and makes her way back up cliff, where she informs the group that Eugene is fine. As she tries to lead the group forward, Rapunzel demands to know what exactly they are getting themselves into. Adira explains to the group how the Moonstone Opal had overtaken the once glorious former kingdom, and King Edmund tried to destroy it. When that failed, he ordered everyone to evacuate the kingdom, while he stayed behind to defend against anyone who would seek out the stone. Meanwhile, he sent Quirin, Hector, and Adira into the world to stop anyone from seeking it out. Adira went back on her mission and sought out the Sundrop, thinking that it could help save her kingdom.
Edmund introduces Eugene to his ancestors, and explains how they have guarded the Moonstone from anyone who wished to take it for their own nefarious purposes. Edmund says that Eugene must fulfill his ancestors' legacy by defending the Moonstone against all who may seek it, including Rapunzel. Eugene begins to wonder if anything in his life meant anything, and ponders what to do next.
Adira leads the group to the entrance to the castle. When the doors open, she sees Eugene, and asks him to let them in. Eugene, somberly, tells Rapunzel that he will not do that, and signals to Edmund to cut the chain that holds the doors open. Rapunzel bangs on the doors, pleading with Eugene to let her in. Adira explains that there is another way into the castle, underneath the castle through tunnels of lava. Pascal sneaks into the castle and makes Eugene realize that he fulfilled Demanitus' prophecy of betraying Rapunzel by keeping her from her destiny.
Rapunzel and the group make it through the tunnels and into the palace. Cassandra suggests that Rapunzel and her go in and fight Edmund, while Adira says she and Rapunzel should. Thinking back to all the times she made Cassandra doubt herself and her judgment, Rapunzel says that she and Cassandra will go in first. Edmund knows they're there and a battle ensues between the group and Edmund, who uses the ghosts of his ancestors to assist him. Eugene arrives and rejoins Rapunzel, fighting his father alongside her. Edmund lambastes Eugene for failing to uphold his ancestors' legacy. Eugene counters by inferring that Rapunzel isn't here to bring destruction, but to save Edmund. Lance figures out how to defeat the spirits: destroying the statues from which they were summoned. They do this until one remains. Just as it appears it will strike down Eugene, Edmund destroys its statue, finally relenting.
Edmund allows Rapunzel passage into the Moonstone's chamber. With Eugene and Cassandra by her side, just like they said they would be, they enter the chamber, where the rocks react to the presence of the Sundrop, pointing directly to the Moonstone. A path is created for them to cross, and they finally reach it. Before she does, she goes to Cassandra and thanks her for everything she has done for her and staying by her side despite the hardships they endured. After hugging Cassandra and telling Eugene she loves him, she approaches the Moonstone, which reacts to Rapunzel's presence and removes itself from its cage. Rapunzel reaches out to stone, prepared to fulfill her destiny.
Just as she is about to grab it, Cassandra suddenly thrusts her arm forward and takes it herself. Absolutely shocked, a look of horror on both her and Eugene's face, she asks what Cassandra is doing as her hair stops glowing. As the Moonstone begins to glow, Cassandra angrily declares that she is fulfilling her destiny. She raises the Moonstone and its raw power is great enough to send Rapunzel, Pascal, and Eugene flying backwards across the bridge. The Moonstone, knowing Cassandra does not possess the sundrop, begins to radiate with undiluted power as Cassandra struggles to control it. The walls in the chamber begin to go haywire as Cassandra finally takes control of the stone, driving it into her chest as she screams. The Black Rocks begin to sprout at an unstoppable pace, covering the entire room. The stone begins to drastically change Cassandra's appearance. It completely destroys her armor and replaces it with a dark blue and black outfit made from the rocks themselves.
Cassandra is lifted into the air as the energy of the Moonstone courses through her and envelopes her to the point that her hair changes to bright blue. With one last scream, the Moonstone stops. Rapunzel, Eugene, and Pascal see Cassandra levitate down to the ground. The former handmaiden begins to laugh and tells Rapunzel that she tried to warn her about who she can trust. As Cassandra looks on with rage and anger in her eyes, Rapunzel and Eugene can only watch in abject horror as they lay witness to the fulfilment of Demanitus' prophecy.
- Mandy Moore as Rapunzel
- Zachary Levi as Eugene Fitzherbert
- Eden Espinosa as Cassandra
- James Monroe Iglehart as Lance Strongbow
- Paul F. Tompkins as Shorty
- Kelly Hu as Adira
- Bruce Campbell as King Edmund
- Jonathan Banks as Quirin
- Eugene sings his first solo.
- The caravan is destroyed for good at the beginning of this episode.
- King Edmund is revealed to be Eugene's father, thus making Eugene the Prince of the Dark Kingdom.
- This episode confirms the popular fan theory that Eugene is the long-lost son of King Edmund and the long-lost Prince of The Dark Kingdom.
- King Edmund is revealed to have lost his right arm.
- This is possibly because he lost it when he tried to reach for the Moonstone 25 years before as previously revealed in a flashback in "Beyond the Corona Walls".
- Cassandra turns against Rapunzel and fuses together with the Moonstone, making her the second person to betray Rapunzel after Varian.
- Cassandra's betrayal was hinted at the end of the previous episode, Lost and Found. When Eugene uncovers a piece of paper that reads "At the end of Rapunzel's journey, one of her party shall turn against her." and looks among members of the group, he notices Cassandra smiling sinisterly at Rapunzel.
- This is the fourth time the closing theme "More of Me" is not featured, the previous being "Queen for a Day", "Secret of the Sun Drop", and "Rapunzel and the Great Tree" , which are also hour-long specials.
- When King Edmund and Adira reveal the origins of both the Dark Kingdom and the Moonstone, the lines they use are almost exactly the same as when 'Flynn Rider' explains about the Sundrop in the movie Tangled.
- When King Edmund and Eugene are eating, Edmund says 'Look I didn't want it to come to this' and 'This is an off day for me this doesn't normally happen.'
- These are the same lines Flynn said to Rapunzel when he used the Smolder in Tangled.
- As Eugene reads out the message Demanitus gave him in the last episode, he reads "When Rapunzel enters the Dark Kingdom" when it's actually supposed to be "At the end of Rapunzel's journey".
- When Rapunzel and Eugene are discussing the prophecy, Eugene's sword briefly appears on his back, but is gone again shortly after.