After the events of Sonic Forces, Infinite has returned and is out for revenge on Sonic, his friends, and Eggman. After somehow regaining his powers, he easily defeats them and sends them to another dimension. One that's populated by ponies and other creatures as a whole.

Now with the help of the Mane Six and their friends, Sonic and the others have to think of a way to get back to their own dimension and stop Infinite before it's too late.