A provocative psychological thriller about a mother tormented by a sound it seems no-one else can hear. Increasingly isolated from her family she forms an unlikely bond with one of her students and is drawn towards a strange community who can also hear The Hum… While hosting a dinner party with her husband Paul one night, Claire Kutty (Rebecca Hall), a popular high school English teacher, begins to hear a low hum. Neither Paul, or her daughter Ashley can hear the noise. This seemingly innocuous noise begins causing her headaches, nosebleeds, insomnia, gradually disturbing the balance of her life, though no obvious source or medical cause can be found. But when she discovers that a student of hers, Kyle, can also hear the sound, the two strike up an unlikely and intimate friendship. Finding themselves increasingly isolated from their families and colleagues, they are drawn towards a disparate group led by a charismatic couple, who also claim they can hear The Hum. As Claire seeks to understand The Hum, what started as a support group quickly transforms into something more extreme, with far-reaching, devastating consequences.
