Swiss nurse Johanna Gabathuler (Dominique Devenport) returns heavily pregnant from her Red Cross mission on the Western Front to Davos, where her family runs the "Cronwald" sanatorium. While still in the maternity room, her father orders her illegitimate daughter to be taken away from her – for the sake of honor. Johanna is to marry the influential politician Thanner (Sven Schelker..

The elite escape the global conflagration at the traditional New Year's ball in the “Cronwald”. This brings Johanna (Dominique Devenport) closer to Dr. Mangold (David Kross). At the same time, Johanna is supposed to complete a mission as a spy at the ball and find out what the Entente – the wartime alliance of England, France and the Russian Tsarist Empire - is up to in the o..

Johanna (Dominique Devenport) and Ilse (Jeanette Hain) find out what is meant by "Mission H": the Entente wants to attack the German Reich from Switzerland with the help of high-precision time fuses. Johanna's job is to prevent the Swiss army's coding device required for "Mission H" from falling into the hands of the Entente. Dr. Mangold also wants the coding device. Bu..

General Taylor's (Cornelius Obonya) sudden departure makes Johanna (Dominique Devenport) worthless as an informer for the German Secret Service. Ilse (Jeanette Hain) gets the order to eliminate Johanna. But Johanna sees through the trap and takes precautions. The General instructs Dr. Mangold to recruit Johanna as an informant. But to protect her - unaware that Johanna is spying for the other..

The Entente searches for the traitor behind an explosion of the time fuses. Dr. Mangold (David Kross) is first tasked with investigating Johanna's fiancé Thanner. In conversation with him, Mangold learns that Johanna (Dominique Devenport) is the only one who has been his guest recently. Meanwhile, Johanna is instructed by Ilse to ensure that the "Lenin Plan" runs smoothly. The..

Johanna (Dominique Devenport) and Dr. Mangold (David Kross) want to start a new life together and get out of the spy game. But as Mangold prepares to escape, he gets captured. Ilse tells Johanna that she has seen her together with Mangold and accuses her of treason, as the Russian Tsar's secret service has learnt of Lenin's presence in Davos and the German Secret Service’s “Len..