Continuity Goof: Shelter Bay is a real city along Lake Superior, in the state of Michigan. It is both a resort town and marina housing many boats. Lake Superior is large enough to have the size fish Mrs. Stone and Jeff were trying to reel into the boat. It is due North of Illinois, where Hilldale is suppose to exist.
Dr. Stone says Shelter Bay is 3 hours away by car, when trying to talk Mrs. Stone into using the boat for the week. Unfortunately this statement can't be true, as Chicago, IL (which is suppose to be North of Hilldale) is over 6.5 hours South of Shelter Bay, and thus Hilldale would be further, yet, from Shelter Bay.