Wonderfully tantalizing. I love the way you keep this story unresolved at either end. Ivo (an effective and believable OC) doesn't know how Severus and Minerva arrive at the camp or what happens to them after they leave (although I'm betting that Harry does). There's a great deal of wartime authenticity about this story, drawn from the memory of a man who chooses to keep certain private details of those two months to himself. Rationing of magic; growing indifference to the lack of privacy; crowds forming around someone with a recent newspaper; repetitive work assignments that give life meaning and structure; isolation from the rest of the world--quite realistic. Your Severus and Minerva are marvels of economy in word. I adore their mutual tenderness.
Favorite line: "I'll set about alienating Merlin himself," he said, "if that fucking Potter dies before he bothers to deliver us all from this nightmare."