Starts off lightly enough, with Toby getting the help of Danny the troll taxi-driver in containing an infestation of Barghests, and then going to a birthday party. Just a day in the life of a half-fae PI. . . .
It's when she gets a phone call from the frantic mother that the birthday boy, and a sibling, have vanished, that things pick up. Tybalt corners her to let her know he's calling in his debt: she must find five children who vanished from the Court of Cats. And Quentin shows up, frantic, to tell her his girlfriend has vanished.
His human girlfriend. All the rest of the children were fae, or partly so. This means that the problem is the Wild Hunt.
And then her Fetch shows up. This is not good news.
Unraveling this all involves a candle, a Mother Goose rhyme, horses disguised as motorcycles, the ballad of Tam Lin, a black rose that a mother sends her daughter, her Fetch driving like a maniac, a road that you bleed to go on, and using iron and silver both as weapons.