1917. War is in its darkest phase. Everyone knows victory can only come at a long, slow, and painful cost. So many lives have been lost that now men previously exempted from military service – because of their age or because their jobs were considered vital to the war effort – are called up. We hear the stories of three of them: the black Glasgow shipbuilder Arthur Roberts (Nathan Stewart-Jarrett), sent into the Battle of Passchendaele; Duff Cooper (Henry Lloyd-Hughes) the dashing and debonair lover of Lady Diana Manners (Tuppence Middleton), the daughter of the Duke of Rutland; and Londoner Ted Poole (Gerard Kearns), just 18 and the last of his fathers' sons left alive.