A Skulk of Foxes - Tales of the City, #3

With peace finally restored to the realm, Arabella is haunted, unable to come to terms with the violence of her actions in defense her family, and plagued with a nagging sense that she is no longer the person she once was, and beyond redemption. When Zoraya and Gareth disappear, everyone but Arabella knows the why and the wherefore of it all, but realises she alone will hold their salvation in her hands, and that there is a price to be paid for one's actions no matter how well-intentioned they might have been. Alone she steps into the web between the worlds, vast and endless permutations of every moment in Space and Time, that co-exist and intersect with the Reality we know.
There, she must find the centre of it allin the roots of the Bone Castle... Qara-al-Ossa...and to save them she must go in-between everything, from whence no living thing can ever return, unaware that Kerissa and her own father have managed to follow her, with the help of a trice of magical foxes sired by Zoraya's own Hasan