Two young British soldiers during the First World War are given an impossible mission: deliver a message deep in enemy territory that will stop 1,600 men, and one of the soldiers’ brothers, from walking straight into a deadly trap.
In 1917 during World War 1, Corporals Schofield (George MacKay) and Blake (Dean-Charles Chapman) are tasked with an incredibly dangerous mission: cross the previously German-held territory to get to the British who are chasing after the retreated Germans to tell them to call of their attack: it’s a German trap and all of the soldiers – including Blake’s brother – will die. The two make it far into their journey, but Blake is killed by a downed German pilot. Schofield continues on, nearly dying multiple times, and is finally able to reach Colonel MacKenzie (Benedict Cumberbatch) and give him the message, and the attack is called off, saving over one thousand lives. Schofield then goes and tells Lieutenant Blake (Richard Madden) about his brother, and then goes and rests under a tree.
During the First World War in April 1917, the Germans have pulled back from a sector of the Western Front in northern France. General Erinmore briefs two young British soldiers, Blake and Schofield. Aerial reconnaissance has spotted that the Germans are not in retreat but have made a tactical withdrawal to their new Hindenburg Line, where they are waiting to overwhelm the attacking British with artillery. With field telephone lines cut, Blake and Schofield are ordered to hand-deliver a message to the Second Battalion of the Devonshire Regiment, calling off their planned attack, which might cost the lives of 1,600 men including Blake’s brother Joseph.
Schofield and Blake cross no man’s land and reach the abandoned German trenches. These turn out to contain tripwires, which a rat triggers. The ensuing explosion almost kills Schofield, but Blake digs him out. They arrive at an abandoned farmhouse, where they witness a dogfight. The German plane plunges into the farm and Schofield and Blake attempt to save the burned pilot. Schofield proposes to mercy kill him, but Blake has Schofield fetch water for the pilot. The pilot stabs Blake and is shot dead by Schofield, who comforts Blake as he dies, promising to complete the mission.
Schofield is picked up by a passing British unit. A destroyed bridge near the bombed-out village, Écoust-Saint-Mein, prevents lorries from crossing, so Schofield crosses alone on the remnants of the bridge. This draws an attack by a German sniper across the river. Schofield tracks down and kills the sniper, only to be knocked out by a ricocheting bullet.
Schofield regains consciousness at night. Fired upon by a German soldier, Schofield stumbles into the hiding place of a French woman with an infant. She treats his wounds and he gives her his canned food and his canteen filled with milk from the farm. Continuing, Schofield is twice discovered by German soldiers. He strangles one and pushes past the other who is too inebriated to stop him. Other soldiers give chase but he escapes by jumping into a river.
Schofield reaches the Battalion just before the British attack begins. Failing to stop the start of the attack, he sprints across the battlefield, after realising that the trenches are too full of soldiers for him to make it to the commander in time. He forces his way into meeting Colonel Mackenzie, and the attack is called off.
Schofield then locates Joseph – who was among the first attacking wave but is unhurt – and delivers the news of Blake’s death. Joseph is upset but thanks Schofield for his efforts. Schofield asks to write to Blake’s mother to tell her about Blake’s heroics, to which Joseph agrees.
Schofield walks away and sits under a nearby tree. The film ends with Schofield looking at his photos, and the viewer learns that he has two young daughters and a wife at home.
The entire movie is filmed as one continuous shot from start to finish with characters moving from place to place in real-time.
In 1917 during the first World War, Corporals Schofield (George MacKay) and Blake (Dean Charles-Chapman) are sleeping under a tree when they are awoken by a sergeant, who asks Blake to pick another soldier and report to his superior. Blake grabs Schofield and they walk through the trenches, wondering what they’ve been asked to do – Blake hopes to be home by Christmas.
They arrive at General Erinmore’s (Colin Firth) quarters. He assigns them on an extremely important mission – he wants them to cross over former German territory – they have retreated in order to get an extremely important message to Colonel Mackenzie, who is chasing after the retreating Germans in order to finish them off. Erinmore explains that this is a mistake – the Germans are luring the British troops into a trap, and they will be decimated. Erinmore has picked Blake because his brother is in the troop that will be attacking, and this mission puts his life on the line. Blake, determined to save his brother, agrees instantly to the extremely dangerous mission.
Blake and Schofield leave immediately through the trenches until they find Lieutenant Leslie (Andrew Scott), and give him their orders to cross. Leslie thinks it’s an insane idea, but gives them instructions and directions on how to get through the former German line. He gives them a flare gun to indicate that they have survived if they make it.
Blake and Schofield make their way through the empty battlefields full of wire, muddy trenches, and then a massive super trench filled with mud and bodies. Schofield’s hand gets caught in the spiked wire, injuring it badly – he wraps the injury and moves onward. Eventually, the two finally finish crossing the space between and arrive at the German trenches, which are empty and abandoned.
They go inside the underground and find the German barracks empty and crawling with rats. Blake finds a tripwire, and before they can react, one of the rats crossing the wire, causing a huge explosion that buries them underground. Schofield is fully buried, but Blake manages to wake him up and get him out so they can flee before the entire barracks collapse. Once out, Schofield angrily asks Blake why he picked him to on this mission. Blake explains he thought they were just going on a food run, he never thought it would be this mission. Blake fires the flare off.
They continue onward, finding a green area. Schofield tells Blake they’ll likely get a medal for this. Blake says it will be nice since Schofield lost his previous one, but Schofield tells him he didn’t lose it but swapped it for wine. Blake is shocked he didn’t take the medal home, but Schofield tells him he hated leaving before. The two come upon cherry blossoms, which Blake knows because his mother has an orchard where he and his brother picked cherries.
They then find a house in the field, which they check but find no one in. Schofield finds a crow and fresh milk, which he fills his canteen with. The two soldiers witness a dog fight in the air between three planes, which ends with the British shooting the German plane down – and it heads straight for them. They run out of the way as it crashes, and pull the burning German pilot out of the cockpit. Schofield suggests putting him out of his misery, but Blake tells Schofield to get him water. As he does, the German brutally stabs Blake in the gut. Schofield shoots the German and desperately tries to get Blake patched up and move him, but it’s too late. Blake begins bleeding out, and tells Schofield to write to his mother and tell her he wasn’t scared. Schofield promises him, and tells him he will finish the mission before Blake dies.
Shortly after, more British soldiers arrive. Captain Smith (Mark Strong) tells Schofield that they are passing through and can take him some of the ways to his destination. He advises Schofield not to dwell on the loss of his friend. Schofield rides in the back of a truck with some rowdy soldiers. When the truck gets stuck in the mud, he leads them in pushing the truck. Once they get back in, he tells them his mission. Schofield gets dropped off a river that he must cross to get to his destination, and he comes under gunfire. He manages to race into the building where the shooter is, and the two shoot each other – Schofield kills the German, but he is hit in the helmet and knocked unconscious.
When he awakes, it is night, and the town is lit by fires. He dodges gunfire as he races through the burning town, eventually stopping to hide in a building where he finds Lauri (Claire DuBurcq), a woman who only speaks French hiding in fear. Schofield speaks French and tells her he’s not German. She tends to some of his wounds and reveals there’s a baby she’s watching over. Schofield gives it some of his milk, and Lauri explains she has no idea who its parents are. She begs him to stay with them, but he explains he must continue his mission. He goes back out into the firefight, having to kill and flee in order to survive. Being shot at, he dives off a cliff into a river, which he fights to survive in. Eventually, the river calms, and he reaches land, where he breaks into sobs.
He keeps going until he hears singing, and sees a group of soldiers sitting around listening to another sing. He sits and listens, then tells a soldier he’s looking for the 2nd. The soldier tells him that’s them, that they’re following the larger group. Schofield runs forward into the trenches, begging someone to listen to him not to go forward with the attack, which no one will – it’s too late, the battle is starting – the first wave is sent. Schofield realizes the only way to reach MacKenzie fast enough is not to take the trenches, but instead run sideways across the active battlefield, which he does. He survives and gets back into the trenches and finds Colonel MacKenzie (Benedict Cumberbatch), who at first refuses to listen to him, in full disbelief and insisting they are about to defeat the Germans. Schofield pleads with him to read the letter, which he finally does – and he orders his men to stand down.
Schofield goes to the medical tents looking for Blake’s brother. He eventually finds him (Richard Madden), unharmed. Schofield breaks the bad news to him about his brother and gives him some of his belongings that he took with him. Blake is devastated, but pulls himself together and tells Schofield to get some food for himself. Schofield asks if he can write to their mother, and he agrees. He tells Blake that his brother saved his life. The two shake hands, and Schofield goes and finds a tree to sit under. He takes out a photo of his wife and of his children, looks at them, then closes his eyes.