When a minor criminal is murdered in the smallest residential square in London, elderly heiress and landlady Celeste van Duren recruits two of her tenants to investigate. Her cleaner, Audrey, knows everyone and is liked by all, while failed writer Lewis is known by no one. He hates his job and his life, and he’s not that fond of Audrey either --- but Celeste is persuasive. As they hunt for clues in and around the Square, they discover everyone has something to hide, including their fellow residents. Audrey and Lewis must find a way to work together if they’re to find the killer in their midst. Assuming, of course, there’s just the one.