On the way to a big family celebration, where Klösschen is allowed to bring his friends Tim, Karl, and Gaby, the Sauerlich-Jaguar gets stuck in a terrible snowstorm. A run-down inn becomes their salvation. There, Klösschen's Uncle Kurt, Aunt Linda, and their cousin Hedwig Müntefering with her husband also find themselves stranded. The connection to the outside world is cut off, the phone line is dead, and the innkeeper seems anything but trustworthy. After a turbulent evening filled with family disputes, the domineering Hedwig Müntefering discovers the next morning that the extremely valuable family seal ring has been stolen from her jewelry box. It turns out that everyone present has a motive for the theft. The culprit is therefore among them. TKKG begins their investigation, unaware of the danger they are putting themselves in. After a lecture at the university, Karl waits for his father and warms up in the empty university library when he witnesses an attack: a man in a skull mask delivers a brutal punch to a student and flees. Tim, Karl, Gaby, and Klösschen get involved, and soon it becomes clear that the incident is connected to an invention by two physics students, Paul Wenzel and Dominik Lechner. Their groundbreaking physical experiment could upend society—which, of course, doesn't sit well with the powerful. Unfortunately, TKKG also find themselves in the crosshairs of these overpowering adversaries. There is no turning back; TKKG must bring the truth to light, no matter the cost!.