Caitlyn returns to Vi when she hears her humming - the same song that Powder is singing in the very first scene of Arcane episode 1. The final clue as to what happened to Jinx at the end of Arcane ...

But the fight scenes in Arcane are staggeringly good ... everything might suddenly resemble a charcoal sketch, or the kind of drawing Powder would have made if given an infinite supply of crayons ...