Summer Gathering, when the rebels of Shadowfell are planning to challenge the evil King Keldec, is approaching rapidly. Caller Neryn, with whom we have made a long journey, still has two Guardians to go before her training is complete. But the White Lady, Guardian of air, is not in the best state. The Master of Shadows(fire) is a trickster who may or may not advise her on how to protect the rebels' Good Folk allies from cold iron, which makes them sick and can kill them. Worse, Keldec now has his own Caller, who is less scrupulous about what he does to the Good Folk he calls. Neryn's beloved Flint, the rebels' double agent, known to his comrades as Owen Swift-Sword, is fed up with his life at court and what he's forced to do as an Enforcer, but has no choice. Can he trust his closest friends in the Enforcers or not?
The story which has built up over the last two books has come to a dramatic climax. Neryn has to make some decisions she doesn't necessarily like. At the same time, she meets people from the other side whom she can like and respect - even finds herself, at one point, pitying the king and wondering what he might have been like under other circumstances. She does some unexpected things which provide an interesting twist to the story - I won't say what they are due to spoilers, and how she gets around some of the impossible problems at the end is especially interesting. I wasn't expecting it, though it's not out of character.
You do tend to forget the heroine is only sixteen, especially in a world where that's an age where you might easily be married, but I think that any teens who have read the other two books will be happy with this one.
Don't read this without having read the first two books, but if you haven't, I do recommend this series. If you're in Australia, ignore the cover of the first book, which is nice if you have sentimental feelings for old-style children's books(I confess I do), but really doesn't suit a YA novel. Just read it. You won't regret it.