When a mysterious orange gloom fills the sky, Iris warns of a new threat: Dark Sparkle Glow! A terrible misunderstanding leads to a broken Moonbow Crystal and an impossible choice. Now, the two teams of Shimmers are separated, trying to do what's right to save Rainbow World. Can they uncover the truth behind the Dark Sparkle Glow and work together again, or is this the end of their friendship and the beginning of the Desolation's reign?