Meet Peter, Janet, Jack, Colin, George, Pam, and Barbara—otherwise known as the Secret Seven! Together with their golden spaniel, Scamper, they have their very own secret society, complete with a hidden shed headquarters, official badges, and a strict password ("S.S.").

It is the dead of winter, and thick snow has blanketed the countryside. When Jack realizes he dropped his official Secret Seven badge near a creepy, supposedly empty old house, he sneaks out in the dark to find it. But instead of just his badge, he witnesses something terrifying: a group of rough men dragging a struggling, squealing "prisoner" into a dark van! The Secret Seven immediately spring into action. Armed with flashlights, snowballs, and their brilliant detective skills, the children must investigate the terrifying ruined mansion, outsmart a grumpy deaf caretaker, and uncover the shocking truth about what the thieves are hiding in the freezing cellar!