Ronnie and his aunt take care of the lighthouse while the keeper is on vacation, and when he does not return as expected, they discover that Tern Rock is a perfect place to spend Christmas

Julia L. Sauer was a writer of children's fiction and a librarian. Two of her books, Fog Magic and The Light at Tern Rock, were among the annual Newbery Medal runners-up. Both are set in Canada, where Sauer frequently vacationed.