Following the events of the Star vs finale "Cleaved," Star and Marco adjust to their new world and begin contemplating the next step of their relationship and their lives. But not everything is smooth sailing. Something went wrong when Mewni & Earth merged, and everything comes to a head with the return of familiar faces, the return of a dangerous foe, and the unearthing of shocking revelations that could change everything for everyone...

It has been five years since Lincoln had returned to the Loud House, being inserted into a new life and new identity. The atrocities committed by Wild Card may not have transpired, but Lincoln is still finding it hard to rebuild himself after the trauma he experienced. But a new threat begins to emerge that will awaken old wounds, and force Link to confront demons from his past. Will Lincoln be able to handle it, or will he be destroyed? How will his family help, and it is already too late?

Ten years have passed since Lincoln's disappearance, leaving his family broken beyond repair. Lynn continues to hold onto hope that her brother is alive. Having now become a police officer, she is working hard to help those in need to make up for her past mistakes against her long-lost brother. But soon, a dark enigma named Wild Card will emerge from the Underworld, and has set his sights on Officer Loud. Now she must protect her remaining family and get to the bottom of why this madman is targeting them, and how he is connected to Lincoln's disappearance.