Eclipsa is now the queen of Mewni, after Star willingly ceded the throne. Under her rule, the living conditions of the monsters have greatly improved. However, the Mewmen parts of the kingdom have fallen into disrepair and the people blame the royal family for their situation. Star, River and Marco, meanwhile, have been searching for Moon, but to no avail. They receive a tip that she is at a local "Pie Festival", only for it to turn out to be yet another false lead. However, afterwards they discover that the pies from the festival were made using Moon's recipe, finally giving them a genuine clue.
After having skirmished with a number of dangerous monsters, Star Butterfly arrives on Earth to live with the Diaz family. However, rather than living a normal life, Star continues on having to battle villains both throughout the universe and in their high school, although if only to protect her extremely powerful wand, an object which she is still confused with.