Actually, the answer is no great mystery, but I won't spoil it. A French traveling salesman discovers a French singer in Russia who is a natural talent. Unfortunately, the singer has amnesia and has no idea who he is. The salesman puts a mask on the guy, bills him as The Unknown Singer and he becomes a hit all over Europe. But will his identity remain a secret when he performs in Paris? The plot is wafer thin but enjoyable for what it is. As would be expected by the title, there is a lot of music, so if you're a fan of 30s French music, this should be right up your alley. The singer was played by Lucien Muratore, who was a famous French opera singer at the time. His voice is fine but he is kind of a stiff in the movie as is the actress who plays his love interest. The movie is enlivened, however, by the presence of Jim Gerald, who plays the singer's manager and a young Simone Simon (of Cat People fame) who plays the reporter assigned to find out the singer's identity. Co-written by Henri-Georges Clouzot, but this is a far cry from his later masterpieces.