The inhabitants of the bottom of the bay are discouraged. So much waste accumulates there. Not a day goes by without one of them getting stuck in a plastic object. Molly and Frédou, two lobsters, and their friend Céleste the crab decide to take action, especially as Molly is about to moult and must think about protecting her eggs. So, they return all the waste to where it came from. Then, in a sudden turn of events, the fishermen intervene too.