The man who hired Nadia Vasiliou to open a wall in Istanbul doesn't survive the morning.

A restoration architect commissioned to assess a sealed 17th-century caravanserai in Eminönü, Nadia arrives before dawn to find something hidden behind a false wall in the sub-basement — and then finds her client dead on the rooftop above. The police rule it accidental. Nadia knows it isn't.

What the wall conceals is a three-century-old register: the complete survival record of a secret religious community that has lived hidden inside Istanbul since 1688, under Muslim names, in Muslim neighbourhoods, maintaining its faith and its records in a script no outsider can read. Someone has protected this secret across four decades and at least three deaths. That someone knows Nadia is in the city. That someone knows who she is.

If she cannot expose the person behind the killings before the archive vanishes from Turkish jurisdiction, both the community's history and the truth about her client's death will disappear with it.