My name is Siobhan O'Connor, but everyone calls me Shy. Two days ago, I was an ordinary sixteen-year-old girl living quietly in Boston with my dad. Today, I'm three thousand miles away from home, and an ancient stone monument has decided I'm the new Defender of Ireland.

That isn't nearly as awesome as it sounds, because now Maeve, the Queen of the Sidhe, is trying to kill me. Dad never told me his father was the leader of the White Branch, a mystical band of warriors tasked with keeping Maeve at bay for the past two thousand years.

Now Grandpa is dead, and Dad has to take his place. But I've made a terrible mistake, and the sword Dad needs to defeat Maeve is bound to me instead. Dad is now her prisoner, and Maeve is using him as bait to lure the rest of the White Branch to their deaths.

This is all my fault, and it's up to me to fix it. I have to find the hidden entrance to the Otherworld, sneak into Maeve's fortress, free Dad and escape, before the traitor within the White Branch allows Maeve's army to invade our world. Maeve's exiled son has offered to show me the way, if I agree to help him in return. I know he can't be trusted, but I need all the help I can get. If we're lucky, we'll be able to rescue Dad and lock Maeve away in the Otherworld forever. If not, Maeve will kill us all ... or make us wish she had.