It is 1958 and Andy's sister is born. While his father insists the baby is 'not quite all there' and his mother sinks into lonely despair, Andy's rope-maker grandfather teaches him the knots that keep treasures safe. When a young painter is hired to decorate their house, Andy's mother finds herself called back from her grief. Then, at the family's seaside retreat, Andy is left in charge of his baby sister on a windswept beach where he discovers not all treasures can be kept safe forever.