The story is about a round object that is unhappy because it is missing a piece. It goes on a journey singing a song as it searches for its missing piece. It tries different pieces but they do not fit. Eventually, it finds a piece that fits perfectly, making it complete and happy. However, when moving very fast with the piece, it can no longer sing its song. It realizes being complete also means accepting its incompleteness, and continues its journey while singing its song.