Nicolas Feuz and Marc Voltenauer have written a crime fiction series centered around two Swiss law enforcement officials: Norbert Jemsen, a prosecutor from the canton of Neuchâtel, and Andreas Auer, an inspector from Vaud. Their second novel, Imperium, was published on August 27, 2026, by Istya & Cie, following the release of their first novel, Ultimatum, on February 27, 2025. The story is set in Switzerland and follows the investigation into a criminal organization that has infiltrated the Swiss Federal Railways (CFF), which is involved in the distribution of a fictional drug called Crackmeth—a blend of crack cocaine and methamphetamine. The authors describe their writing process as a collaborative effort in which they allow each other to take control of the narrative, characters, and settings. This method, they explain, creates a "third voice" by blending their individual styles through continuous interaction and friction in their writing. To facilitate this process, they prepared a detailed script divided into chapters, allowing either author to write any given chapter. This structure helps maintain consistency and coherence across the series. The plot of Imperium revolves around two separate incidents: a man found projected under a train in Neuchâtel and a violent confrontation in the Gotthard tunnel. These events lead the protagonists to uncover the existence of the criminal organization operating within the CFF. To ensure the plausibility of the fictional drug Crackmeth, the authors consulted Pierre Esseiva, a specialist in drug analysis, who provided insights into its potential real-world feasibility. The series challenges the common perception of Switzerland as a country of order and tranquility by exploring the possibility of serious crime within its borders. Feuz remarked that "Switzerland is not cleaner than other countries that surround it," highlighting the contrast between the nation's reputation and the darker realities depicted in the novels. The authors plan to continue the series with a third novel, Infernum, scheduled for release in 2027.