On the fifth day after a witch is born, a ritual is performed to facilitate her use of magic in years to come. The new witch is kept in a windowless room and out of starlight for the five days. After the ritual is complete, she's presented to the goddess, exposed to starlight and her soul is bestowed. But there's a serious side effect to the witches ritual. A doppelganger is created. The one infant becomes two, but only one child has the power channel magic. The doppelganger, a soulless shell, is then to be killed by the mother to protect the witch child. But sometimes, somehow, the doppelganger survives.

A skilled Hunter, Mirage has recently accepted a commission to investigate the death of a powerful key witch. During her search for the killer, Mirage discovers that the victim had been keeping track of her whereabouts for years. As she has always avoided contact with witches and their servants, Mirage is not only curious but angry at the discovery. Feeling her connection with the victim, an unlikely coincidence, Mirage prepares to carry out the rest of her commission on her guard.

On the verge of claiming her powers, Miryo prepares for the Elemental trials that face every novice and makes ready for her future as a witch. Miryo faces the four elements and comes through her tests unscathed, but when she faces the Void, which represents wholeness of self, she comes undone. At her failure, the Primes, the witches who lead the various castes, realize that Miryo's doppelganger is alive and send her to kill the double. A witch can only realize her full potential if her doppelganger is destroyed, and the death of one can only come at the hands of the other.

A fully realized new world, Ms. Brennan's first novel is a brilliant read. The conclusion is a humdinger I never saw coming and literally stopped reading and said "Wow!" when it hit me. With likable characters, good world building and a story arc that keeps you wanting more, everything fits together nicely and comes to a satisfying conclusion for characters and readers alike.