How far would you go to keep a secret?

It's a secret for a reason.

Mai Fisher's mother died when Mai was five years old.

Or did she?

Nearly 30 years after Mai's mother and father were executed as spies by the Taiwanese Secret Police, Alexei Bukharin learns that Katherine Maitland, Mai's mother, may have survived by defecting to the People's Republic of China.

He and Nelson, his former partner, now the head of the United Nations Intelligence Directorate, will get to the bottom of the rumor. Whatever the truth is, they decide Mai should never learn that truth, even if that means eliminating anyone who knows the secret.

Then, post-9/11, Mai has to review the personal papers of Roisin O'Saidh, her business manager and victim of the collapse of No. 2 World Trade Center. But in a secret room in the attic of a Maitland house in Dublin, Mai and Alexei find the diaries of Roisin's predecessor, Roisin's mother Eithne O'Saidh.

Mai realizes these diaries will show her who her mother was and delves into them.

Alexei, however, needs to find out what Eithne knew about Katherine Maitland's "death," the secret he has sworn to keep from Mai at any cost.