Molly and her friend Emma find more letters as they prepare their own video project on the Great War. At first, they think the letters are stuff Molly's father has packed away in boxes under the attic eaves but they find an unfinished and un-sent letter from Susan that persuades them to intervene in time by writing a letter to Tom. He is desperately ill. Their letter gives him the will to survive. The girls don't know how the loop in time works but they look up Einstein's theory of time and hope for the best.