This is SUCH a middle school book :-D
A spooky story about a power-mad woman who steals children's souls. I liked that it was set against the backdrop of children escaping the London blitz and ending up in a far more dangerous place. The story did get a bit convoluted at times, as the Lady's past dealings with the Magister were brought in little by little. Also, Kat is a clever girl, but seemed to stumble upon magical solutions a bit too easily.