Germany, 1945. The soldiers who liberated the Gross-Rosen concentration camp said the war was over, but nothing feels over to eighteen-year-old Zofia Lederman. Her body has barely begun to heal; her mind feels broken. And her life is completely shattered: Three years ago, she and her younger brother, Abek, were the only members of their family to be sent to the right, away from the gas chambers of Auschwitz-Birkenau. Everyone else--her parents, her grandmother, radiant Aunt Maja--they went left.

Zofia's last words to her brother were a promise: Abek to Zofia, A to Z. When I find you again, we will fill our alphabet. Now her journey to fulfill that vow takes her through Poland and Germany, and into a displaced persons camp where everyone she meets is trying to piece together a future from a painful past: Miriam, desperately searching for the twin she was separated from after they survived medical experimentation. Breine, a former heiress, who now longs only for a simple wedding with her new fiancé. And Josef, who guards his past behind a wall of secrets, and is beautiful and strange and magnetic all at once.

But the deeper Zofia digs, the more impossible her search seems. How can she find one boy in a sea of the missing? In the rubble of a broken continent, Zofia must delve into a mystery whose answers could break her--or help her rebuild her world.