Yossi Kleinmann is an uncharismatic and under-appreciated history professor lecturing on political leaders in totalitarian regimes. Neither his students nor his domineering wife Sarah show him any respect. In order to celebrate the 90th birthday of Sarah's grandmother Oma Gerda, a Berlin-born Holocaust survivor, the extended family is spending the Sabbath at a hotel. Due to an unfortunate shaving-mishap, Yossi gets stuck with a Hitler-mustache after the Holy Sabbath came in. As a religious Jew, Yossi can't take it off on the Sabbath, while his wife and his in-laws get extremely upset knowing that this image would surely evoke a heart-attack with Oma Gerda. Torn between guilt and family pressure, Yossi joins the festivities while trying to hide the mustache from Oma Gerda. However, the events take a surprising turn when Yossi slowly but surely goes through an unexpected transformation...