For a decade, Hannah's life has been pretty close to perfect - she has a great job, she's married to Mark, and her child-free existence means she's free as a bird. The only sadness in her life is a fall-out with her sister Diane, who hasn't spoken to her in over ten years. But now Diane is on her doorstep - and this time, she's got her teenage daughter Mia in tow. When Diane asks if Mia can stay with Hannah and Mark for a few days, Hannah is glad of the chance to get to know her niece. But as the days turn into weeks and Diane doesn't return, Hannah begins to worry. Why hasn't her sister been in touch? Diane is carrying a devastating secret that will destroy Hannah's carefully constructed life. But how much is she willing to reveal - and when will she pick her moment?