Summertime at Wansett Point, on the sea, starts off with a haunted house mystery for Gail Netherby, but turns into something of a far more personal nature when Gail discovers Nanette, an orphaned girl with a peculiar attachment for old Cobbler's Knob. On practically her first exploration of the old house, Gail, who is an adopted child, finds Nanette, who has been living in Wansett Point with a welfare lady and whose comings and goings to Cobbler's Knob have provided the ""hauntings"". Understanding Nanette immediately, Gail promises not to tell about her and the two girls become firm friends. Further detecting proves Nanette's real connection with the place through former family ties but the real problem is Nanette's future when the welfare lady can no longer keep her. The Netherbys almost decide to adopt her but an even happier and more sensible solution is provided through another lady who has already come to Nanette as her own. Though Cobbler's Knob is inundated by high tides, it becomes a symbol of the past giving way to a better future.