The third thrilling installment of the middle-grade fantasy series from bestselling authors Garth Nix and Sean Williams.

When an old man in an even older house dies mysteriously, twins Jack and Jaide Shield find themselves drawn into a dangerous treasure hunt in some deep, dark places. Jack and Jaide are troubletwisters -- gifted with magic and cursed by The Evil, a force that will stop at nothing to destroy their world. The old house holds something very important to The Evil -- and Jack and Jaide must race to find it, even though they don't know what it looks like or where it is.

Jack and Jaide aren't the only ones searching for the treasure. And as the mystery gets bigger and bigger, they're not sure who they can trust. Even friends are beginning to act suspicious. And their father, who should be their strongest ally, is leading them into treacherous territory.

At the heart of all magic is mystery, and at the heart of this mystery is nothing less than the key to controlling magic. It's going to take the two troubletwisters to the edge of their Gifts in order to figure this one out.