Private Investigator October "Toby" Daye is a changeling, a half-human, half-fairy woman, who feels out of place in both worlds. After a particularly nasty spell turns her into a fish for fourteen years, she has lost contact with her human fiancee and her daughter, no longer possesses a PI license, and is trying to lay low, far away from both fairy and human entanglements. This changes when her old friend fairy Countess Evening Winterrose leaves a message on her answering machine, charging her to solve her murder, and cursing her to make sure she cannot refuse. Toby will literally die if she is unable to solve Evening's murder in a certain amount of time.
So Toby has to come out of hiding, and start investigating. She needs to find out why Evening was murdered in the first place, and who could have been brutal enough to both shoot her with iron bullets and sever her throat with an iron knife. She has to get back in contact with a number of fairies, some less sympathetic to her cause than others, and solve the murder before the curse, or Evening's killer, catches up with her.
Toby is a cool heroine. It's easy to see why she would choose to isolate herself and try to stay far away from both fairies and humans who knew her, having been badly burned by both sides of her heritage. It is made very clear that the half-human changelings often have a hard time of it, never really being accepted fully in the fairy world. Toby had a surprisingly honoured position before she was turned into a fish on a mission, but feels she let her liege lord down, and has a hard time admitting that maybe she made some mistakes by cutting herself off completely from people who loved her upon being turned human again.
Unlike a lot of paranormal heroines, Toby is not that powerful. She has some magic due to her fairy mother, but it wears her out when she uses it, and isn't always helpful. She actually gets hit worse by Evening's curse specifically because she uses some of her magic, and most of the time she has to rely on brains and mundane weapons to fight her foes.
There are a number of fascinating characters in the book. Evening was clearly a very impressive lady, from what is revealed after her death. Toby also realizes that she only knew a tiny bit about her, and that she may have been overly judgmental about many things. Tybalt, the King of Cats, who loathes Toby because of her half-human blood, yet will keep his word to her anyway, was delightful, and the various fairy hideouts all over San Fransisco were very nice. Like Holly Black, Melissa Marr and a number of other writers of fairy-themed paranormal fantasy, McGuire manages to blend the Fay and Human worlds nicely, explaining why most humans never realize the supernatural world all around them.
The book was a bit slow at first, but as the action got going, I was hooked. I will be picking up the sequels to this to see if the series stays as good, or hopefully, gets even better.