Catalina is a Spellcaster-in-training in the 37th Dimension, aka The Dimension of Magic, who can never get the spells right. Despite encouragement from her familiar, a cat named Icky (short for Ichabod), she lacks faith in herself and fails her test to become an official Spellcaster.
Meanwhile, the Dark Wizard Zorr invades Spellcaster HQ to obtain the very powerful Scepter of Dynamic Influence. If he succeeds, it’s game over. In an effort to prove herself, Catalina snatches the Scepter and zooms off on her trusty broom Broom. Zorr inadvertently damages the Scepter just as Catalina uses it to get “as far away from here as possible”.
Catalina and Icky arrive in the 3rd Dimension and crash-land in a landfill in central New Jersey - without magic OR the Scepter. They head to the nearby small town of Darring in the hopes of figuring out a way home. Unbeknownst to them, Zorr has also been brought here, but to prehistoric times. He uses his mystic amulet to return to the present - but to the Swiss Alps.
In the sky over Darring, the Scepter bursts out of a dimensional rift and plummets to somewhere on the edge of town. Catalina and Icky’s search for the Scepter leads them to the house of librarian Ed Forrester, his 20-something niece, his tween nephew, and their dog Garroway - who can now talk. The Scepter had crashed in their backyard, which transferred the magic into Ed and Garroway. Catalina warns them of the perils of pure magic via The Tragic Tale of Todd - a nerdy Spellcaster-in-training who tried to use the Scepter and paid the ultimate sacrifice. Catalina attempts to fix the Scepter, which opens a portal to the pocket dimension of pure magic inside the Scepter.
Zorr can also feel the pure magic, which convinces him the Scepter must be on this world. He teleports to Darring, where the pure magic is too much for him. It causes a major backlash of magical energy that sets an apartment building on fire. Catalina, Ed, and the others arrive to help. They discover that Zorr is there and narrowly escape.
As Catalina works on repairing the Scepter, she and Ed discuss the importance of believing in oneself and to keep trying, no matter how times you fail.
The magic spreads and causes all kinds of craziness throughout the town. Catalina runs into Zorr and manages to get away. Zorr tracks her to Ed’s house and attacks. During their magical battle, Catalina smashes Zorr’s amulet, revealing that he is actually Todd. With Todd on the verge of victory, Catalina gets an idea. She and the others vanish in a blinding flash. With no Spellcasters to stand in his way, Todd plans to use the Scepter to rule this dimension.
Turns out Catalina had teleported all of them into the pocket dimension inside the Scepter, saying she wasn’t strong enough to beat Todd. Icky disagrees; she’d acted like a true Spellcaster. They also discover they’ve all become infused with pure magic, which may be the key to defeating Todd. Catalina teleports them back to finish the job.
They arrive to find magic running amok throughout the town, and set out to fix as much as they can. Catalina faces off against Todd. Finally confident in herself, she proves to be his equal and casts a spell that overwhelms him with the pure magic and makes him vanish - for good.
Catalina sets everything back to normal. The magic retreats back to the 37th Dimension. She and the family exchange goodbyes before the portal closes.
Back in the 37th Dimension, Catalina is made an official Spellcaster and uses the Scepter one last time before returning it to its proper place. Icky asks “What did you do?”
As the family gazes up at the night sky, wondering if they’ll ever see Catalina & Icky again, Garroway regains the ability to speak.