Lucy arrives back home after taking a nightly stroll with her pet bat, Fangs, and as she heads upstairs, she sees the siblings painting the bathroom pink (her least favorite color). The others tell her that during their last sibling meeting (which she failed to attend), the siblings all decided to paint the bathroom pink instead of black.
Later on, Lucy is trying to summon a spirit with the pets, but as she tries to summon it, she is interrupted by Lori chatting with someone on her phone, Lincoln playing an online game, and Lynn playing paddleboat with Lana, Lola, and Lily. Lucy tries to tell her siblings to quiet down, but Lily simply smacks her away with the paddle.
At dinnertime, Lynn Sr. reveals that there's one last piece of pie left, and asks who wants it. Lucy raises her hand, but Lola dashes across the table to obtain it, ignoring the fact that Lucy raised her hand first.
In the living room, the siblings arrive to watch TV. Lucy grabs the remote, and turns on The Vampires of Melancholia. However, the siblings reject the idea, and Lana takes the remote from Lucy to watch an audition show. Lucy complains that she had the remote first, but Luna informs her that they also decided on what to watch during the sibling meeting (which she also failed to attend). Furious, Lucy tries to vent out her anger with a poem, but her book is accidentally destroyed by one of Lisa's spilled chemicals.
Unhappy with her siblings' neglect, Lucy retreats to the attic, only to find it is also filled with their property. While cleaning away the clutter, she comes across an old chest belonging to her Great Grandma Harriet, and discovers a spell book inside a secret compartment. Happy with the find, she decides to use the book to take revenge on her siblings. Reciting spells from the book, Lucy disables Lori's phone, renders Lana unable to sit, due to an itchy butt, and curses Lisa with literal sticky fingers. Unfortunately, the plan backfires, when most of her siblings compromise, with Lori simply inviting her friends over to talk, Lana using Edwin as a butt-scratcher (to Lucy's irritation), and Lucy herself getting stuck to Lisa.
In her frustration, Lucy stumbles across a more powerful spell in the spell book. As Lucy tries to summon the spell, Lincoln and Luan arrive to ask Lucy if she wants to visit Pop-Pop, but she politely declines. Once the rest of the family leaves, Lucy sets to work preparing the spell, sprinkling her siblings' beds with a magical substance that will render them voiceless.
The next morning, the spell appears to have worked, as all of Lucy's siblings have become mute, much to her delight. Lucy takes advantage of their missing voices, by making them paint the bathroom black, get all of the leftovers, and watch her show, all while nobody can backtalk her.
Eventually, Lucy realizes that the spell has taken a horrible toll on her siblings. Lynn was kicked out of the rowing team for being unable to commandeer her team, Lincoln can't communicate with his friends over his online game, resulting in their characters getting killed, and Lori's friends believe she's giving them the silent treatment, thus ending their friendship. Lucy, back in the attic, admits that she didn't mean to ruin their lives, and discovers that in order for the spell to be broken, she must transfer the curse to herself.
In Lori and Leni's room, Lucy admits casting the spell on the siblings, and only wishes to fix things. However, the siblings (silently) laugh at this, explaining that her spell didn't make them lose their voices. It turns out that during Pop-Pop's shuffleboard match the previous day, they cheered so loud, they lost their voices from laryngitis, or the inflammation of the vocal cords in the larynx. It is also revealed that the "spells" Lucy summoned didn't actually happen. Lori's phone had a low battery, Lana accidentally rolled around in poison ivy, and Lisa becoming sticky was actually because she spilled one of her formulas. Lucy then apologizes for her misdeeds, and her silent siblings apologize to Lucy as well, and decide to make her feel better by watching her favorite show with all of them, much to Lucy's joy.
In the attic, Lucy decides to put the spell book away, and tells Great Grandma Harriet that even if the others don't listen to her that much, she still loves them. After she leaves to catch up with the others, the frown on the photograph of Great Grandma Harriet Lucy found mysteriously changes to a smile.