All The Broken Places by John Boyne TPB

1946. Three years after a cataclysmic event which tore their lives apart, a mother and daughter flee Poland for Paris, shame and fear at their heels, not knowing how hard it is to escape your past. Nearly eighty years later, Gretel Fernsby lives a life that is a far cry from her traumatic childhood. When a couple moves into the flat below her in her London mansion block, it should be nothing more than a momentary inconvenience. However, the appearance of their nine-year-old son Henry brings back memories she would rather forget. Faced with a choice between her own safety and his, Gretel is taken back to a similar crossroads she encountered long ago. Back then, her complicity dishonoured her life, but to interfere now could risk revealing the secrets she has spent a lifetime protecting.