The Four-Story Mistake — Elizabeth Enright

It's a house full of secrets--and it's all theirs!

Mona, Rush, Randy, and Oliver Melendy have lived in the city their whole lives. How can they move to a house in the country that they've never seen? But what their father says goes, and soon they're on a train to the Four-Story Mistake -- an old almost-mansion full of places to hide, old stories to uncover, and more adventures than the Melendys could have imagined!