One day at school, Luz finds Gus by himself feeling down. He is upset because he messed up after trying to help Willow with a pixie problem. By using illusions he caused the pixies to attack Willow. Because of this, Gus has lost a little confidence in his ability to perform illusion magic, and feels he should try something different. The next day, Luz comes over to Gus' house for help. She needs to use his library card to look up the human who lived on the Isles as well see Amity. Along the way, they witness a Slitherbeast rampaging through the town. It almost attacks a child, when three teens intervene and help capture the beast. They are Glandus High students named Bria, Gavin, and Angmar. Gus is amazed by them, that he goes up to talk to them. Mattholomule then shows up with a map for the Glandus High students, leading to the Galderstones. According to them, they are powerful relics protected by a guardian. Many witches have sought for them but all returned empty handed. Bria, Gavin, and Angmar are planning to seek out the stones with Mattholomule. They offer Gus the join them. At first he hesitates, but Luz manages to encourage him. And to help him out, she supplies him with some of her glyph cards.
While Gus is out on an adventure with the Glandus High students, Luz goes to the library. There she discovers the name of the human was Philip Wittebane who donated his diary to the library. Luz finds Amity, who happens to be an employee at the library, and asks for her help in finding the diary. According to her, the diary is probably kept in the forbidden stacks, along with all the other old books. Unfortunately, only Malphas the master librarian is allowed in, but that does not stop Amity from helping Luz. However, they have to be sneaky about it otherwise Amity could lose her job at the library.
Meanwhile, Gus, Mattholomule, and the Glandus High students are in the Fore Arm forest searching for the Galderstones. It is said that these stones can boost a witch's spell whenever they hold one. The Glandus High students have big plans for those stones. Angmar wants to grow an entire forest to create a butterfly sanctuary, Gavin wants to create the biggest abomination to impress his father, and Bria hopes to make life at Glandus High a lot better because there weak students are pushed around by the strong. The kids arrive at their first challenge, which is a huge wall of thorns blocking their path. They all encourage Gus to clear the way for them, and he does this by using the fire glyph. The Glandus High students are impressed, but Mattholomule has his eyes on him. Back at the library, Luz and Amity are searching for Philip Wittebane's diary while at the same time hiding from Malphas. Turns out, he gave Amity her job at the library and her own study. According to her, he is usually nice, but he would feed them to the bookworms if they got caught. On the Isles that would be an unholy blood sucking snake monster. Luz tells Amity a bit about the human realm and promises to someday show it to her. Not wanting to get her into trouble, Luz suggests they should head back, but Amity insists on finding that diary.
Back in the woods, Gus, Mattholomule, and the Glandus High students make it to a place where they discover ruined statues. Among them are the Galderstones. However, Gus discovers these ruins are actually a cemetery for illusionists, and the stones belonged to them. Gus says they should not take them, but the Glandus High students pay no attention. Suddenly, the guardian appears, and the Glandus High students put him out there to fight it. Gus Realizes he is out of glyphs. So, he uses an illusion of the guardian to scare it away, only to discover it too is also an illusion. The caster is an old man who is the keeper of the Looking Glass Graveyard. Realizing the guardian is a fake, the Glandu High students trap Gus and the keeper while they loot the Galderstones. After being treated badly by them, Mattholomule helps free Gus and the keeper. Together, they use powerful illusions to chase away the Glandus High students and take back the Galderstones. The keeper considered permanently sealing away the Looking Glass graveyard, but Gus and Mattholomule instead convinced him to let them help improve the place's defenses on weekends.
Meanwhile, After a long time searching, Luz and Amity find Philip Wittebane's diary, only to discover the pages have been eaten by a mouse. Luz cannot hold in her anger and shouts at it, alarming Malphas. Disappointed, he kicks the two of them out and fires Amity. Luz tries to apologize, but Amity is not up for it at the moment and sadly heads home. However, Luz is determined to make things right and heads back into the library. After a series of harsh trials, Luz was able to convince Malphas to give Amity's job back. She arrives at Blight Manor, all beaten up, to bring back Amity's staff card. Upon seeing Amity, she has changed her hairstyle from her usual green to lilac. The mouse that ate the diary had followed Luz, and Amity points out that it is an echo mouse, which can playback all the knowledge it consumes. The mouse becomes a projector and plays a vintage piece of footage from the diary. Told mostly in silhouette, Luz and Amity learn about Philip Wittebane beginning his journey to harness the powers of the demon realm and build a portal back to his world. The clip ends and Luz says that she hopes she and the mouse can become good friends. Amity says that should not be a problem since she has a way of getting into people's hearts and kisses Luz on the cheek. Both are left in a state of shock. Amity hurries back into her house all flustered, leaving Luz in disbelief.
- Sarah-Nicole Robles as Luz Noceda
- Alex Hirsch as King
- Mae Whitman as Amity Blight
- Tati Gabrielle as Willow Park
- Issac Ryan Brown as Gus Porter
- Harvey Guillén as Angmar
- Nik Dodani as Gavin
- Felicia Day as Bria
- Erica Lindbeck as Emira Blight, Green Girl
- Ryan O'Flanagan as Edric Blight
- Jorge Diaz as Mattholomule
- Roger Craig Smith as Warden Wrath
- Fred Tatasciore as Malphas, Slitherbeast
- Kevin Locarro as Braxas
- Alex Lawther as Philip Wittebane
- Christopher Swindle as The Keeper
- Eden Riegel as Pink Butterfly Illusion
- Kari Wahlgren as Blonde Kid
- Dee Bradley Baker as Guardian, Gavin's Dad Illusion
- The title is, of course, a reference to Lewis Carroll's Alice Through the Looking Glass.
- The name of the human who once lived on the Isles is Philip Wittebane, who lived in the 1600s and the one who created the portal door to the human realm.
- The old rundown house in the woods which the portal door opens back and forth between the two realms might be Philip Wittbane’s home.
- Amity admits that Luz's arrival changed her; thinking and feeling things that she never did.
- Its confirmed Amity dyed her hair; she changes it to a shade of purple (likely to match Luz's hoodie).
- Luz becomes aware of Amity's affection for her.
- This is the first episode where Eda, King, and Hooty are all absent. However, King does appear in a crystal ball recording, and Eda in a newspaper article.
- Luz speaks Spanish for the sixth time:
- "No te preocupes. Todo va a salir bien." translation "Do not worry. Everything will be fine."
- "Nada funcionara a menos que lo haga funcionar." translation "Nothing will work unless you make it work."
- The coded message, on the base of a statue in the forbidden stacks, translates to "Strings".
- Mattholomule says he has an older brother.
- The names on the statues refer to members of the crew, color designer Mari Alizor, and prop designers Aleth Romanillos and Khari Cephas.
- Gus is revealed to have moved up two grades at Hexside in this episode.
- During the final scene, the sunset is the colors of the bisexual pride flag. Also, Amity's staff card has a shooting star on the back that has the colors of the lesbian pride flag.
- When Bria runs out of the Looking Glass Graveyard, she isn't wearing her gloves
- Eden Riegel is credited for voicing Bocha in the episode's credits despite Boscha not appearing.