During the First World War, Stefan Brandt (Jai Courtney) is sent to be the personal guard of the German Emperor Wilhelm II (Christopher Plummer). The Kaiser lives in a Dutch castle and after the invasion, the German authorities are worried that the Dutch spies could follow him. As Brandt begins to infiltrate Kaiser’s life to find clues, he finds himself attracted to a passionate relationship with Mieke (Lily James), one of Kaiser’s men.
He soon discovers that Mieke is Jewish and has hidden this to avoid the Holocaust. A local SS officer informs Brandt that there is a British agent who provides information from a neighboring village to be investigated. Mieke is also an informant who reports to a pastor in the city about what is going on in the Kaiser’s house. When Heinrich Himmler (SS leader Eddie Marsan) decides to come to an unannounced visit with a large platoon of SS soldiers, Brandt is forced to choose between following his heart or following the line of the Nazi party.
Wilhelm’s wife discovers that Mieke and Brandt have an affair and tells Wilhelm this, waiting for him to fire Mieke and scold Brandt. However, Wilhelm supports the love they share, and on several occasions he even told Mieke about a woman he loved a lot before marrying. When the time of the house’s search arrives before Himmler’s arrival, Brandt personally looks for Mieke’s room.