This gripping five-part drama follows a tense police surveillance investigation into a tight knit Manchester community and explores whether it is ever possible to observe the lives of others with true objectivity and zero effect.

Claire, a popular English teacher, begins to hear a low humming sound that no one else around her can hear. This seemingly innocuous noise gradually upsets the balance of her life, increasing tension between herself and her husband, Paul, and daughter, Ashley. But despite multiple doctors, no obvious source or medical cause can be found.