Meet Leo, a quiet boy with extraordinary ears who loves to listen to the world around him – the rustle of leaves, the distant train whistle, the secret murmur of the river. One quiet afternoon, while exploring the creek bed, he discovers a smooth, grey pebble unlike any other. This pebble doesn’t just sit there; it hums with a soft, beautiful, magical tune! To Leo’s astonishment, the pebble reveals itself to be a ‘Humming Beastie’ named Hum, who has become separated from his family and lost his way to the legendary Great Resonance – a hidden valley where all the most wonderful sounds in the world gather and harmonize.