Ghost Exile book 5. There are serious spoilers for the earlier books ahead.
It start in media res. Caina and all are plotting to infiltrate the location known as the Inferno to retrieve the loremaster. And Nerina nearly destroys everything with her conviction that she saw her dead husband alive. . . .
They regroup and go on. Caina finds that someone leaves odd knives outside where she is staying, now and again. It involves kidnapping a man by convincing him there's a plot against him, someone asking what color a messenger's eyes are, arming smiths with hammers, an old enemy of Caina's being confused with her, why the Desert of Candles is called that, what, exactly, is Nasser's story, and more.