Peter, Janet, Jack, Colin, George, Pam, Barbara, and Scamper the dog are incredibly excited for the upcoming Guy Fawkes Night. They have been working hard for weeks, building a magnificent, life-sized "Guy" dummy and pooling all their pocket money to buy a spectacular box of colorful rockets and sparklers. They lock their precious fireworks safely inside their garden shed headquarters, eagerly awaiting the big night. But disaster strikes when they arrive to find the shed has been completely ransacked, and their entire fireworks collection has been stolen!

At first, the Seven suspect Jack's mischievous sister, Susie, of pulling a cruel prank, but they soon realize a much more dangerous gang is at work in the neighborhood. While hunting for their stolen sparklers, the children stumble onto a serious string of local burglaries, and the ruthless thieves are using the chaos, loud explosions, and glowing fires of Bonfire Night to perfectly cover their tracks! Packed with midnight sleuthing, creepy disguises, and a thrilling confrontation in the dark, the Secret Seven must catch the crooks before their celebration goes up in smoke!