Hallam Square starts in 1858 when Annie Hallam has at last found complete happiness. She has three healthy children and adores her husband Frederick. After years of struggling to make a living in the small Lancashire town of Bilsden, Annie knows she deserves to sit back and enjoy her life - after all, she's not yet forty, still in her prime.
But worries - at first faint clouds on the horizon - are imminent. Frederick has been looking pale and ill lately. Her brother Tom hasn't moved on after the death of his young wife. Rebecca, her half-sister, is longing for something more than her work at the salon. And William, her son, isn't happy at university. In spite of Frederick's gentle urging not to take the burdens of the entire Gibson family on her shoulders, Annie can't help feeling concerned.
And something much more dangerous is looming - a threat not only to Annie's peace of mind, but to her life as well.