1942.

After her fiancé is killed in a pogrom, Hannah Martel narrowly escapes Nazi Germany and takes temporary refuge with her cousin, Lily, in Brussels.

Safe for now, but desperate to flee Europe for good, Hannah joins the Sapphire Line: a secret resistance network led by a mysterious woman named Micheline and her enigmatic brother, Mateo.

Freedom is tantalisingly close. But when Lily's family are arrested and slated for deportation to Auschwitz, Hannah finds herself torn between her loyalties and her own determination to escape . . .

How much is Hannah willing to sacrifice to save the people she loves?