The secret that concerns Naomi's mother revolves around her absence and why she never returned to Naomi.  For so long, it had been something that was never fully addressed or answered for Naomi, a silence that enabled her own mind to blame herself or victimize herself for her mother's absence.  This proves not to be the case.  Naomi's mother never returned for she was in Japan during the dropping of the atomic bomb and lived through the horrific events of such a catastrophically brutal instant.  The secret was her living through the atomic blast and eventually dying from it.  It was shrouded in secrecy as seen as something that neednt be spoken or articulated.  Yet, in learning of the secret, Naomi is able to appropriate it and speak to it from a position of strength, no longer letting the silence of the secret emotionally disfigure her as her mother had been disfigured by the blast.  Naomi is able to overcome this silence and accept it as part of her past, being able to speak to it from a position of strength and understanding in the refusal to be victimized by it as the truth is known and grasped.