In Secret Seven Fireworks, it comes to the knowledge of the gang that Susie has made her own detective gang. Susie is Jack’s sister, and she often disrupts the gang’s secret meetings. She is not liked by the gang at all, and they do everything possible to keep her away. After learning of Susie’s new ‘detective gang, the Secret Seven are furious. Shortly afterwards, they learn that some money has been stolen. Their primary suspect in the case is Susie, who is always looking for ways to sabotage the gang’s plans. However, they wonder if Susie would stoop to such lows. Thus, they go on a money hunting trail, trying to nab the real culprit. The story has actual showdowns between the seven teenage kids and Susie and her gang.