On 6 April 1917, aerial reconnaissance has observed that the Imperial German Army, which has pulled back from a sector of the Western Front in northern France, is not in retreat but has made a strategic withdrawal to the new Hindenburg Line, where they are waiting to overwhelm the British with artillery. In the British trenches, with field telephone lines cut, two young British lance corporals, William Schofield, a veteran of the Somme, and Tom Blake, are ordered by General Erinmore to carry a message to Colonel Mackenzie of the 2nd Battalion of the Devonshire Regiment, calling off a scheduled attack the next morning that would jeopardise the lives of 1,600 men, including Blake's brother Joseph, a lieutenant.
