Forgetting is the most evil spell. The grown-up Alice lives a less fairy-tale life and stops dreaming, which means that everything about the Wonderland is disappearing. People in the Wonderland even forget why they exist, and before everything dissipates, the Cheshire Cat casts a phantom spell to find Alice, hoping she could save the Wonderland once more.
But the Cheshire Cat can't remember the spell, and a wrong spell made him travel to a parallel world, where the Alice here doesn't even know the existence of the Wonderland.
In order to make the Wonderland not to be forgotten, the Cheshire Cat brings Alice from various parallel worlds back to the Wonderland, trying to awaken people's memories. Despite having experienced failure again and again, the Cheshire Cat still believes that he will find the right Alice.