Cayeux is a small seaside town in northern France with a huge pebble beach. In winter, it's as deserted as the moon. In summer, however, a crowd of regulars and vacationers swarm over the beach. At one end of the beach, there is a pebble processing plant where Marie works. She is young and pretty.
Her boyfriend Paul works at the grocer's in the winter and as a lifeguard in the summer. Paul's sister works in the local casino which is where his mother Rose goes to fritter her pension money away in slot machines. Paul doesn't understand Marie's dreamy temperament and stifles her with his awkward love. Marie senses a growing unease within herself.
The vacationers that she sees over the seasons remind her that her youthful dreams lie elsewhere. She wants to leave to fulfill them, and she gets the chance when Albert, her young boss at the factory, gets fired and his sports car offers a tempting escape.