A legendary serpent living in the river Ter eats local livestock and people. A boy named Pere steals a diamond from the serpent's nest in the forest. When the serpent returns and finds the diamond stolen, it uses its powers to track Pere by scent. Pere hides the diamond under a mortar, and the serpent wraps around the mortar, squeezing until it is exhausted and dies. The diamond is then offered to Our Lady of the Spring.