Book 5 of the Ghosts. spoilers ahead for the earlier books.
This one opens unusually, without Ghost business. Caina offers to take the five-year-old Nicolai to see the ships while his parents are busy. This means she is there when the invasion begins. . . .
His parents, at home, hear the screams, and Ark ends up organizing the nearest soldiers to fight.
It involves a bargain made a sword's point, an old enemy, a brother who does not want to believe that his sister practices necromancy, something that happened to Caina in the earlier books being revealed, a question of gates, stormsingers, and more.