Castle Falcon

Katie and her brother Zach have spent their whole lives in the vast and ancient stone fortress called Castle Falcon, somewhere in the northwestern U. S. Their mysterious father, driven by secret fears, rarely allows them to leave the safety of the Castle and venture out into the world.

Katie, thirteen, and Zach, twelve, are constantly testing the boundaries of their enormous gilded cage. When they finally crack the secret of opening the hidden rooms their father had sealed against their curiosity, they aren't ready for what they find: living hearts in jars, people turned to stone, and a cage containing something terrible and invisible.

And that's before they discover a buried gateway to a dark and demon-filled hell, and the monstrous creature that guards it...

Katie and Zach thought their summer would be boring. Now, with the help of some strange new friends, they may have to save the world!

Full disclosure: along with the Castle, the book has secret caves, a few wizards (mostly retired), an evil demon in disguise, a spaceship, wormholes, talismans, a dragon, a sea monster, a giant spider, a talking lizard, an alien princess from a lost kingdom, a number of small faeries, Rodents of Normal Size, a healthy dollop of Cthulhu mythos, a small touch of gourmet cooking, a really big gun, lethal teddy bears, a fart joke, and one (1) gratuitous mooning of an authority figure. There is no specific mention of a kitchen sink, but there is a utility sink that has an important role.