Based on a recent novel. After notification of some sort of war/invasion the adults disappear or are taken from a farmhouse. The kids (two older and two younger?) hide in a shed but are found and separated by the military. The 2 girls go looking for the boys and are eventually re-united (in a Camp?). One of the boys has become keen on fighting. Ends back at the farm. I keep thinking the title is "The Way Back" or "The Way We Were" or some such. Thanks.