"Over Sea, Under Stone" is a fantasy novel by Susan Cooper, published in 1965. It is the first book in the Dark is Rising sequence and follows the adventures of the Drew siblings—Simon, Jane, and Barney—who are on a quest to find a magical artifact known as the Grail. Set in a coastal village in Cornwall, the story intertwines elements of Arthurian legend and ancient mythology. The children discover that they are part of a larger battle between the forces of Light and Dark. Guided by their mysterious friend, Will Stanton, they must decipher clues and confront dark powers to protect the Grail from falling into the wrong hands. The novel explores themes of bravery, friendship, and the struggle between good and evil.