In the scorching summer of 1976--the hottest on record--Christopher Norton, his wife Laura and their young daughter Faye settle into their new home in north London.The faded glory of the Victorian house is the perfect place for Norton, a composer of film soundtracks, to build a recording studio of his own. But soon in the long, oppressively hot nights, Laura begins to hear something through the crackle of the baby monitor. First, a knocking sound. Then come the voices.For Norton, the voices mark an exciting opportunity. Putting his work aside, he begins the project of a lifetime--a grand symphony incorporating the voices--and becomes increasingly obsessed with one voice in particular. Someone who is determined to make themselves heard . . .