Jonah and Katherine are siblings in today's world. When last we saw them, they had just discovered that Jonah (and several other kids) were actually children that had been abducted from other times and places and placed in this century. In Sent, they, along with their new friends Chip and Alex, go back in time to the 1400's a time where being a royal was dangerous to one's health as people double crossed even (or especially!) family members in order to seek more power and wealth.
OOH, dontcha just love it! Well, what are you waiting for? Go to your library and get it. Pop the popcorn. Pour the cherry coke. And get ready for a lovely adventure.