Simon, Jane, and Barney Drew are looking forward to their month-long holiday in the quiet sea village of Trewissick. Along with their parents, the children are sharing a rented house with Great Uncle Merry, a kind but mysterious man. Strange things always seem to happen when he is around, and this holiday is no exception.

While exploring the house one rainy day, Barney discovers an ancient manuscript with a map sketched on it. The siblings think it is the start of a fun treasure hunt, but then some of the residents of Trewissick begin to show interest in the map…a lot of interest. Now, the children find themselves being pursued by a menacing group of people who want to know where the map leads. Simon, Jane, and Barney confide their secret to Great Uncle Merry who is well aware of the map’s true value and the treasure it leads to. He is also aware that the quest the children have set upon is more than just a treasure hunt, it is a deadly battle of good verses evil.

Over Sea, Under Stone, by Susan Cooper is the first book of The Dark is Rising sequence.