After being released from a camp for political prisoners in 1935 Nazi Germany, Arnold Clasen returns to Hamburg to lead a quiet life.  He contacts Renate, with whom he is still in love.  And, although he is aware of the danger of doing so, he begins a friendship with Walter, who is active in the resistance.  But as old comrades are arrested one after another, Arnold begins to suspect that Walter, who remains unscathed, has betrayed them.  Your Unknown Brother is a landmark film exploring the role of the individual in confronting anti-fascism.