An unknown and swiftly spreading disease is ravaging the animal kingdom, threatening it — and humanity — with extinction.

All over the world, animals are mysteriously dying. Veterinarians observe the same symptoms: unexplained prostration, tears of sadness, and a song of distress.
Shan, a virologist, sets off on a crusade against the disease, which is now attacking mankind. Only individuals suffering from deafness appear to be resistant. Soon after, Milos Orban, a sound engineer and leader of an activist group, contacts her. According to him, the source of the global disaster is the "hum": a noise only perceptible to animals and people particularly sensitive to soundwaves. As this theory becomes increasingly plausible, Shan, too, begins to hear strange noises.