A Swiss/German co-production mostly filmed in Austria, "Das unsterbliche Lied" tells the fictionalised story about how school teacher Franz Xaver Gruber and a priest in an Austrian village came to write the most popular of all Christmas songs, "Stille Nacht, heilige Nacht" (aka "Silent Night"). Set in the time of the Napoleon wars, the plot concerns the young Lois (Paul Richte...