When war breaks out in the lull of summer 1914, it surprises and pulls millions of men in its wake. And Christmas arrives, with its snow and multitude of family and army bundles. But the surprise won't come from the inside the generous parcels which lie in the French, Scottish and German trenches.

That night, a momentous event will turn the destinies of four characters; A Scottish priest, a French lieutenant, an exceptional German tenor and the one he loves and sings with, a wonderful Danish soprano. They will find themselves at the heart of unprecedented fraternisations between German, British and French troops.

During that Christmas Eve, the unthinkable will happen: rifles will be left at the bottom of trenches and steps will be taken towards those opposite, to shake their hands, exchange a cigarette or a piece of chocolate, to wish them a "Merry Christmas".