Lucy arrives back home after taking a nightly stroll with her pet bat, Fangs. 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, 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 "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 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, Lincoln can't communicate with his friends over his online game, 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 voice 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.
Since the spell book once belonged to Great Grandma Harriet, it appears as if she was also into occultism, like Lucy is.
This is the eighteenth time Lincoln does not speak to the viewers.
This is one of the few episodes where Luan appears, but does not make a pun when she speaks.
The plot of this episode is vaguely similar to the one in "A Tattler's Tale", in which they both involve a Loud sibling constantly being/feeling left out in their family. Though in this case, Lucy being the odd person out was unintentional.
During Lucy's seance, it's revealed that the Louds had a pet goldfish named Goldie.
A girl who looks similar to Polly Pain appears in Lynn's boat. It's unknown if that's her, or if her character model was reused for a generic background character.
Another girl sitting in front of her resembles Ronnie Anne, but with yellowish brown hair, and with fair skin. This too, may be a modified character model.
This episode implies that magic could exist in the show's universe, albeit in a limited form.
This is the second time Fangs appears in an episode, the first time being "Back in Black".
However, Fangs is much smaller in this episode than in "Back in Black", which could mean that "Spell it Out" takes place before "Back in Black".
This episode reveals that Rita is a member of a book club.
BioShock - Like many of the characters in the game, Lisa recorded an audio diary of her work prior to losing her voice.
Leeroy Jenkins - Rusty Spokes shouts his name before charging into battle in the same manner as the title character of this viral video of a World of Warcraft player who endangers his own team by charging into battle unprepared in a similar matter.
Harry Potter - The title card music is similar to Hedwig's Theme from the Harry Potter film series.
Macbeth - All of Lucy's spells are in reference to Act 4, Scene 1 of this well-known Shakespearean tragedy.
In "Dance, Dance Resolution", Polly has two pairs of eyelashes, but in this episode, she has three pairs of eyelashes.
Lynn's outfit is different from her teammates'.
When the siblings were shaking their heads to tell no to Lucy about not casting a spell on them, Lana's eyelashes were missing.
Lincoln using sign language to tell something, but it gets mistaken for frosting a birthday cake.
Things going wrong without the Loud siblings' voices.
Lucy trying to summon spirits, but it always gets ruined by her siblings.
Lucy casting "spells" on her siblings, but it backfires.
The Loud siblings having meetings without Lucy.
Nobody noticing Lucy (treating her like an outcast).