NOTE: This spoiler was submitted by Jeremy

The film opens with a red-haired witch (Kacey Musgraves) riding a motorcycle with her infant daughter Earwig in tow, singing to her as she rides. She is being pursued by other witches in a car with a sharp-toothed mouth. The red-haired witch pulls off a strand of her hair, which she throws back into the car as it morphs into a pile of worms.

The witch brings Earwig to an orphanage, St. Morwald’s Home for Children, where she can be safe. The orphanage’s Matron (Pandora Colin) and her assistant come across Earwig and see the note from her mother that states that she is being pursued by another coven of witches. Matron finds the name “Earwig” to be unappealing, so she introduces the baby to the other children as Erica Wigg.

Years later, Earwig (now played by Taylor Paige Henderson) is a mischievous girl who seeks excitement. She guides her friend Custard (Logan Hannan) to the top of the building as she scares him with ghost stories. Earwig has no desire to be adopted and hopes that she can stay at the orphanage forever.

The orphanage is visited by a witch named Bella Yaga (Vanessa Marshall), along with her master, the Mandrake (Richard E. Grant). Matron lines up the children to be adopted, but Earwig does her best to seem unappealing so she won’t get adopted. She looks up at the Mandrake and notices him grow in size and take on a more demonic appearance. Bella Yaga takes a look at Earwig and decides to adopt her. Despite Earwig’s protests, she gathers her belongings and finds an old tape from her mother, labeled “Earwig”.

Earwig is taken to Bella Yaga and the Mandrake’s home where she is forced to be the witch’s assistant. When Earwig questions her about Mandrake, Bella orders Earwig to not disturb him unless she wants something terrible to happen. Earwig asks Bella to teach her how to be a witch, but she just makes her do work in her room. Bella also threatens Earwig with worms if she makes her angry.

During her time there, Earwig tries to escape, but finds that the exits have been sealed by the Mandrake. She sees that the Mandrake has little demons that get him whatever he wants, specifically his favorite meals from places around town. Earwig also discovers that the Mandrake is a writer, as she comes across his manuscripts.

In her room, Earwig learns that Bella Yaga’s cat familiar, Thomas (Dan Stevens), can talk and that he is annoyed with being used for Bella’s spells and experiments. Earwig then plays the tape from her mother and listens to a rock song that she played called “Don’t Disturb Me”, which Earwig becomes addicted to. Earwig and Thomas then go into Bella’s spell room and find a spell that can protect them from anything she throws at them. They create a type of rubbing oil and slather it over their bodies before going to sleep and wait for it to take effect.

Earwig once again demands to Bella that she teach her how to perform spells like her, but she still refuses. Although she is angry, she soon finds that the Mandrake isn’t nearly as bad as she thought, since he brings her tea and a snack while she works. She also asks to read some of his work, which he allows (though she later finds it boring). In the meantime, Earwig crafts herself a doll of Bella. She also sees a hole in the wall where the Mandrake watches her and looks into his room where she sees him playing music.

After serving breakfast to the Mandrake, Earwig makes her own spell to give Bella “an extra pair of hands” as she demanded of Earwig, making them grow on Bella’s forehead and back. Earwig laughs hysterically but Bella prepares to make good on her threat with the worms. A pile of worms fall into Earwig’s room, but they don’t affect Earwig or Thomas. She then grabs them one by one and slips them into the hole through the wall that leads into the Mandrake’s room. He becomes enraged, thinking Bella sent them there herself. Bella runs into Earwig’s room to punish her, but Mandrake gets to Bella first. Earwig runs through the now warped hole to Mandrake’s room and finds pictures of himself with a younger Bella and Earwig’s mother. It turns out they were part of a band called Earwig. Bella played drums, Mandrake played keyboard, and Earwig’s mother played guitar and sang. A flashback implies that Earwig’s mother and the Mandrake were romantically involved before she quit the band and fell out with him and Bella. The Mandrake comes into the room to tell Earwig to leave, but she begs him to let her learn how to be a proper witch. He tells Earwig that Bella was once a gifted witch and drummer. Earwig goes to Bella and hugs her when she realizes she isn’t all bad.

Six months pass, and Earwig is learning more on how to be a better witch. Bella and the Mandrake have warmed up to her and are treating her like a surrogate daughter. On Christmas Day, Earwig manages to get Custard to come visit. He is approached by an adult who walks to the house with him. Earwig answers the door and comes face-to-face with her mother for the first time, who tells her, “Merry Christmas, Earwig.”

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Earwig is a 10-year-old child left at an orphanage as a baby by her mother, a witch being chased by other witches. She is adopted by another witch, Bella Yaga, and her master, the Mandrake. Despite Earwig's protests against being adopted, she goes with them.

Earwig is made to be Bella's assistant, but she wants to learn how to be a witch too. She also befriends Bella's cat familiar Thomas. They come up with a spell to protect them from Bella's threat of giving them worms.

Earwig soon learns that Bella and the Mandrake were part of a band along with Earwig's mother before the latter left them. After a few months, Bella and the Mandrake warm up to Earwig and teach her magic. On Christmas Day, Earwig's friend Custard from the orphanage comes to visit, and, to her surprise, so does her mother.