Having stopped the human shipment to Mortmesne, the victor in the invasion of the Tearling during the reign of Kelsea's mother, she now has to decide what she can do to stop the Mort Army. Her commanders know they can only delay, but they do so as much as possible in order to buy Kelsea more time.
Kelsea, meanwhile, though her heart and soul are wrecked with how she can protect her people, her mind is elsewhere. She starts falling into fugue states, which takes her back to the pre-Crossing, to a woman called Lily. Her own identity and emotions becomes wrapped up in Lily and what happens to her.
Meanwhile, there is another mystery to solve: the identity of the Red Queen of Mortmesne. One of the overriding messages of this book (and the last) is the power of names, seen in how Kelsea changed hers to pay tribute to her foster parents, and how the Red Queen is fiercely protective of hers.
There is the issue of identity, too. Kelsea is changing, not only in herself as the ruler of the Tearling, but also in appearance. This causes not little crisis for herself and those around her. Being plagued by her fugue states and the dark thing, who pops up in Kelsea's fireplace from time to time to bargain with her, and her obsession with finding out who her father was, gives her only so much that she can bear.
The dual narrative of Kelsea and Lily gives more life to an already thrilling story, and ensures that the reader has plenty to explore. Sometimes, it can result in a little bit of a book hangover switching from one side to the other, but that just shows how absorbing each narrative is.
Definitely another story to keep the reader up into the small hours.