1917 On 6 April 1917, aerial reconnaissance has found that the German army that has withdrawn from a section of the Western Front in northern France and is not in retreat but has made a strategic retreat towards the Hindenburg Line, where they are waiting to overwhelm the British with artillery. In the British trenches, which have the telephone lines in the field cut, two young British lance corporals, William Schofield, a veteran of the Somme, and Tom Blake, are ordered by General Erinmore to relay an email 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 who were Blake’s brothers Joseph who is a lieutenant.
Schofield and Blake cross in the middle of nowhere to get to the abandoned German trenches however, Schofield is injured in his left hand while crossing the road. Inside an underground barracks they find a tripwire erected by the Germans that is triggered by an escaped rodent and the blast nearly killed Schofield however Blake helps him out, and they escape. They are able to escape an abandoned farmhouse, and they find a German plane is shot down during the course of a dogfight against Allied aircraft. Schofield and Blake help to save the pilot who was burned from the wreckage. Blake convinces Schofield to get water for the pilot. As Schofield’s back is turned, the pilot stabs Blake. Schofield shoots the pilot to death and soothes Blake as he dies, promising to complete the mission , and to write to the mother of Blake’s. In the process of taking Blake’s rings and dog tags along with Erinmore’s letter, he is taken by a passing British unit.
A bridge that is destroyed close to Ecoust-Saint-Mein hinders British vehicles from crossing it the bridge, and Schofield decides to dismantle the bridge. Schofield makes use of the remaining portion of the bridge to cross without assistance, and is then subject to fire from an armed sniper. Schofield and the sniper trade shots, and Schofield fire back. The sniper dies while Schofield is hit in the helmet and knocked unconscious. He awakens at night and makes his way through the flame-lit city’s ruin. After escaping from a German soldier, he discovers an French woman hiding with an infant. She tends to his wounds and he gives her his canned food and milk from the farm. Schofield, regardless of her pleas, resigns when she hears the chimes of the nearby clock, and recognizing that time is running out. He escapes from German soldiers by jumping into the river when being confronted by them. The river transports him as the cherry blossoms begin to fall. As he approaches the riverbank he is swept across the water. He discovers D Company 2nd Devons in the forest. This is the last of the attack. Schofield attempts to get in touch with Colonel Mackenzie as the company advances towards the front.
Realising that the trenches are too packed for him to reach Mackenzie in time, Schofield goes “over the top” and sprints across the open field parallel to the British trench line, just as the infantry begins its charge. Schofield makes his way to Mackenzie to receive the news. Schofield searches for Blake’s brother and finds him, who was among the first wave of attackers and is bloody but unharmed. Schofield informs Joseph of his mission and about Tom’s demise and passes on Tom’s rings as well as his dog tag. Joseph is extremely angry about his brother’s death, but he is grateful to Schofield for his efforts. Schofield asks permission to write to Joseph about Tom’s heroics. Joseph accepts. In a state of exhaustion, Schofield sits under a nearby tree and looks at pictures of his children and wife.