Corni is sad. A wave took away her beautiful pearly white shell. Her friend Achilles will do whatever it takes to help her get it back. First, he dives into the water... but the sea is much too big. They’ll have to drain it if they're ever to find the shell again. Not a moment to lose. With help from passersby and everyone who's ever lost something, Achilles and Corni start draining the sea, taking care not to disturb its inhabitants.