Luz, a self-assured teenage girl, accidentally stumbles upon a portal to a magical world where she befriends a rebellious witch, Eda, and an adorably tiny warrior, King. In order to get home, Luz must help them with a mission.
Luz is a creative and expressive girl, but this causes trouble at her school. After an incident with her book assignment involving live snakes, her mother, Camilla decides to send her to a Reality Check Summer Camp to straighten out her wild imaginative personality. While waiting for the bus to pick her up, a little owl takes her favorite book, The Good Witch Azura. She chases the owl to an old rundown house in the woods where she is immediately transported to a tent filled with weird stuff. The owner is a strange-looking lady who closes the portal behind her when Luz tries to get her book back. The lady reveals herself as Eda the Owl Lady, who happens to be a powerful witch who sells human stuff. She takes her back to her stand, and offers Luz to buy something, like rubber clogs, a deodorant roll, or a TV. Eda becomes impressed with Luz when she gets the TV working, attracting more customers. However, authorities show up and declare both Eda and Luz under arrest. However, Eda gives the law enforcer the slip and flies away with Luz on her magic Owl staff.
Luz learns from Eda that she is in a world called the Boiling Isles, where every myth humans have is caused by a little of their world linking into there's including giraffes ("Bunch of freaks!"). They arrive at Eda's home, the Owl House, and meets her little furry "roommate", King. Eda then brings up the reason why she brought Luz to her home. King was once a mighty king of demons until his Crown of Power was stolen many years ago by the Warden Wrath. Now it remains locked away behind a magical force field that only a human can breakthrough. Since Luz is a human, Eda and King ask her to help them get King's crown back, and in return Eda will send her home. Seeing no choice, Luz complies and accompanies them to the Conformitorium, where people are imprisoned for being unsuitable for society.
Luz and King sneak to the top of the tower, where they meet a lot of inmates who have been imprisoned for being different and do not fit in. Luz feels sorry for them, because she can totally relate. Luz and King later regroup with Eda and find where King's crown is being kept. Luz passes through the force field and retrieves the crown, which turns out to be a kid's meal crown and possess no great value whatsoever, except to King. Before making their escape, they are captured by the Warden Wrath who unexpectedly asks Eda out on a date. She rejects Wrath and fights him with King while telling Luz to leave. Luz then comes back, releases the inmates and helps Eda defeat Wrath. After returning to the Owl House, Eda opens the portal so Luz can return home. However, after everything she has been through, Luz feels like she does not belong there and decides to stay and be Eda's apprentice. Eda accepts, on the condition that Luz has to work for her. Afterward, Luz texts her mother that "camp" is going to be great.