As Chloe settles into her new life with her estranged mother, Catherine, in the vast estate of Tenderville, she discovers a captivating world surrounded by mysterious gnomes and intricate secrets hidden within the mansion's twisting walls. One fateful evening, during what begins as a typical dinner, Chloe stumbles upon a concealed chamber behind a sliding bookshelf. Here, she finds a breathtaking green gemstone known as the Keystone, which she unwittingly transforms into a necklace. This seemingly innocent act opens a portal to another realm, allowing a horde of insatiable creatures called Troggs to invade her quiet life.
While Chloe grapples with the social dynamics at her new school, she forges an unexpected friendship with Brittany, Tiffany, and Chelsea—a trio lovingly dubbed the BTCs. Longing to fit in, she wears the Keystone around her neck, only to have it quickly snatched by Brittany, who is enchanted by its magical properties. Her troubles multiply when she encounters a Trogg lurking in her basement and attempts to confront it, only for it to vanish in a burst of inexplicable energy.
The following day, Catherine reveals that she will be taking on extra shifts at work, leaving Chloe to confront the weird events spiraling around her. Just when she feels overwhelmed, the gnomes—who have been closely observing her—reveal their extraordinary secret: they are indeed alive. The playful Quicksilver and Zook, the gophers' leader, inform Chloe that she has accidentally stolen the Keystone, an artifact that holds the power to control the portals unleashed by the Troggs. They recount their age-old conflict with these creatures, sparked by the Troggs' destruction of the flora that sustains the gnomes' existence.
With the Keystone now in Brittany's possession, the gnomes find themselves unable to prevent the Troggs from wreaking havoc in their world. Zook beseeches Chloe to reclaim the Keystone so that she can seal the portals’ access, organizing their efforts until she is able to retrieve the invaluable artifact. Chloe sets off on this daunting journey alongside her awkward neighbor and classmate, Liam, as they join forces to combat these malevolent beings and unveil the secrets at stake that threaten to unravel their reality.
Amid her shifting priorities—from snagging the necklace from Brittany at a school dance to winning the favor of the elusive BTCs—her relationship with Liam wavers. Afraid that their bond might jeopardize her status, Chloe makes the tough choice to pull away from him, which leads to Liam's departure. However, her plans to reclaim the cherished necklace hit a snag when she learns Brittany did not bring it to the dance. Instead of giving up, Chloe hatches a new plan to sneak into her friend's house.
In a shocking twist, Liam inadvertently gets sucked into a Trogg portal during an unexpected encounter at the dance. Realizing he is missing, Chloe frees herself from the BTCs' influence and resolves to bring Liam back. With newfound determination, she ventures beyond the known, journeying through a toilet portal to join him. Together, they encounter Zamfeer and discover a colossal crystal, hatching a plan to obliterate it using Chloe's phone battery.
Their audacious operation succeeds, and they leverage the rampaging Troggs to facilitate their escape back into their dimension. As the gnomes rejoice over Zamfeer's return, Brittany arrives, intent on humiliating Chloe and Liam by destroying the remaining Keystone. Soon after, a gigantic Trogg emerges from the depths of the basement, ready to disrupt everything.
Blocked from their escape, Chloe and the group are forced to retreat to the rooftop accompanied by an ooze plant—a quirky entity feared by the massive Trogg. Using her ingenuity, Chloe concocts a makeshift bomb from the Keystone, Brittany's phone, and the ooze plant, leading to the demolition of the towering Trogg and the restoration of harmony to their realm.
As calm returns, Chloe wakes beside her mother, reassuring her of her desire to stay with family. Meanwhile, Brittany remains blissfully unaware of the chaos that unfolded the previous night. Reflecting on her adventure with Liam, Chloe rekindles their friendship as they head off to school together, their bond stronger than ever.
