Visiting all the lighthouses on Michigan's Upper Peninsula was not Sam and Becky's idea of an exciting summer -- until they met a ghost who had been haunting the lighthouses for almost 100 years... looking for riddles. While their mom and dad research the lighthouses for a book they are writing, Becky and Sam do their own searching. From shipwrecks to mountain tops to Paul Bunyan's backyard, they follow the trail that leads them along the shores of Lake Superior to Eagle Harbor. But it doesn't take them long to realize that someone -- or something -- is following them. With more questions than answers, Sam and Becky are more determined than ever to solve the mystery at Eagle Harbor.