Kendra and Seth Sorenson are sister and brother. Their maternal grandparents have just died and left an unusual will asking that their children and spouses go on a 17 day long cruise. Since grandchildren aren't invited on this cruise, Kendra and Seth are being dropped off at their paternal grandparent's house for a nice long visit. But there are some strange things going on: Grandpa has some funny rules and where the heck is Grandma?! And why is the caretaker leaving little pans of milk everywhere?And so begins the journey of Kendra and Seth. They discover their grandfather is the caretaker of a magical sanctuary, that those bugs in the garden are really fairies, and that things that go bump in the night really are frightening! The cast of characters grow as we learn more about two warring societies, more secret preserves, etc.I wanted to strangle Seth at times. I have a younger brother myself and boy do I remember growing up and how obnoxious he was! Well, he still is obnoxious, but that's beside the point! Seth's reckless curiosity lands him in hot water, but through being true of heart, he is able to overcome. We get to meet more friends and family members (distant), fairy tale creatures, and fantastical adventures. You get to watch Kendra and Seth come into their own despite their youth. It is truly a rollicking ride!One of the things I loved about the series is that it didn't wan. Usually I find that if a series is longer than a trilogy, book 3 and 4 tend to drag or get muddled. Not in this case! Mr Mull artfully keeps his reader's attention, the plot twisting, the stakes higher, and you read on.