The Blight of Forgetting has become a pervasive threat, its silent grey mist now subtly affecting The Mundane, causing widespread apathy and a loss of shared history. The Echo Collectors are bolder than ever, their hunger threatening to consume all resonance. The Custodians of Aevum realize a desperate measure is needed: the Resonance Song, an ancient melody hidden within the Shifting Isles, capable of re-establishing the deep connection between Aevum and The Mundane.

Leo, Maya, and Finn embark on their most perilous journey yet, venturing to the unpredictable Shifting Isles. Here, elemental energies are wild, and nomadic communities of unique Aevum creatures guard ancient secrets. The children must learn to master these volatile forces, communicate with the wary islanders, and piece together the fragmented parts of the Resonance Song.

But the Echo Collectors launch a major assault, determined to silence the song forever. The Shifting Isles' Song is an epic race against time, where the children must unite disparate factions, brave elemental chaos, and unleash the power of an ancient melody to save both worlds from being utterly forgotten.