The Ardennes, December 1944: the Nazi forces are making their last offensive in Europe - a campaign which will come to be called the Battle of the Bulge. But there is a third side to this battle: an unknown and ancient force which seems to pay little heed to the laws of nature.

Where do the bodies of the dead disappear to?

What is the true nature of the military experiments conduced by both sides?

The Doctor, Sam and Fitz must seek out the truth on a battlefield where no one and nothing is quite what it seems.