Now and Forevermore Arabella

Found abandoned in a Colorado mall when she was too young to say how she got there, the little three-year-old girl wearing a bracelet with the name "Amanda" on it doesn't know anything about herself, not how she came to be left there, not who her parents are, and not even her full real name. 

Nine years of living in foster care later the truth finally comes to light.  Amanda's not an actual orphan at all!  It turns out she was accidentally kidnapped in Florida when one of the antique cars her father sells was stolen while she was in it.  DNA testing proves she's really a missing girl named Arabella Prescott, and her life changes for the better when her terrific parents and adoring little sister arrive to take her home to the island of Farris Key, where just about everybody she meets is thrilled to have her back. 

Yet Arabella has returned to the very island she was kidnapped from in the first place, so alongside the family's joy at their reunion are some very disturbing concerns.  Are the kidnappers, who were never found, island people too?  Who is the odd person who seems to keep watching their house from the beach across the street?  What exactly happened to cause the authoriies in Colorado not to figure out Arabella's identity when there were people all over Florida looking for her? 

And why does a certain nearby house keep giving Arabella the creeps?