Hilda and Frida are in the library to do research on the Ahlberg family. They find it suspicious that the librarian is nowhere to be found, and even left a cart of books unattended. When they look for her in the secret room that Hilda discovered back in “Chapter 8: The Tide Mice”, they discover another secret room. From this room on, the girls keep finding one secret passage after another, each leading to a new room deeper underneath the library, one of which is filled with ancient spell books. Along the way, Frida also finds a card that the Librarian dropped.
Eventually, they end up in an underground structure occupied by witches. Frida realizes they found the legendary Witches Tower (which according to most stories is in the Huldrawood). Hilda realizes in turn that this means the librarian must be a witch, and she is proven right. They see the Librarian as the uses a magic portal to enter the room of The Committee of Three. The girls eavesdrop on the conversation, and thus learn the librarian has only two hours left to reclaim the book “The Skeleton Whisperer”, which was checked out almost 30 years ago and hasn’t been returned. If the book is not reclaimed in two hours, the Librarian will be cast into the Void of No Return. When the Libriarian realizes she lost the card with the name of the person that borrowed the book, Frida and Hilda reveal themselves to return the card. The last borrower was Matilda Pilqvist. The Committee is shocked to see non-witches in their tower, and even consider throwing them all in the void right away, so the Librarian quickly drafts to Hilda and Frida to help her get the book back.
The Librarian reveals she already knew Matilda Pilqvist had the book, but was afraid to visit her. Matilda Pilqvist was one of the strongest witches ever, and to find her one has to navigate a hazardous maze. The Librarian takes a wand from the frame of a portrait of Mathilda, and opens the door to the maze. The three protagonists find themselves in a room with a plant creature, which Hilda unsuccessfully tries to fight with a sword, until Frida figures out the sword is actually the key to the next door. What follows is a dangerous quest full of obstacles and puzzles, most of which are solved by Frida.
Eventually, they reach a snowy landscape, where they are confronted by a creature made of lava and rock. The Librarian offers to fight the monster while Hilda and Frida go through the final door. Behind the door, they suddenly find themselves in a normal living room. It turns out Matilda Pilqvist is the elderly lady whose doorbell Hilda rang when she was hanging out with Trevor and his friends back in “Chapter 3: The Bird Parade”. Matilda in turn reveals that the monster outside is not dangerous; he is her gardener Eldrid. It is also revealed that the Librarian’s name is Kaisa, and that she was Matilda’s student. She was afraid to face her old teacher because she has trouble remembering spells, and has thus failed as a witch. Matilda however is proud that she became the keeper of books. Matilda does not know where the book they came to look for is, but Hilda figures out her familiar, Cornelius, ate it. After they make him vomit up the book, Matilda teleports them all back to Witches Tower.
Unfortunately, they arrive a minute too late. Hilda, Kaisa and Frida are sentenced to the void, but Matilda defends them by pointing out their various accomplishments while navigating her maze. During the arguing, the gate to the void stays open for too long, and the creature living there emerges into Witch tower. It drags Hilda, Frida and Kaisa into the void, along with several book cases. With Frida’s help, Hilda locates a book that contains a spell Kaisa can use to contain the void creature. It’s not enough however, so Frida uses a spell to open a portal, and brings the plant creature they encountered earlier into the void, as well as the sword. Hilda keeps chopping up the plant to make it grow faster, and soon it overgrows the void, subduing it. With the danger over, Matilda reveals Frida has the potential to become a witch, and offers her to become her student. Frida accepts, and Hilda will be her familiar. But first, they will have tea and board games back at Matilda’s house.
- The Librarian is named Kaisa, and is a witch.
- The old lady that appears in the "Chapter 3: The Bird Parade" is named Matilda Pilqvist, is an Arch-Sorceress, and was the master of Kaisa.
- This was one of two episodes screened at NCYIFF 2020, the other being "The Troll Circle".
- This is the fourth episode where David does not appear, although he is mentioned. It is also the first time that he is absent for two episodes in a row.
- Twig is likewise absent but gets mentioned.
- Witches Tower is under the Trolberg Library.
- Frida starts learning magic with Tildy to become a witch.