It is April 6, 1917, somewhere in Northern France, and two young British soldiers are summoned to receive a very important mission. The German army has pulled back from the Western Front to a defensive position called the Hindenberg Line. Aerial reconnaissance has determined that this movement of troops isn’t a retreat but a tactical withdrawal and their new position is heavily fortified with artillery. Chasing after them would effectively be walking into a trap. The problem is, a British battalion is preparing an assault without this knowledge, and communication with them has been lost. The only hope is for two messengers to cross No Man’s Land and deliver the order to stand down.
The two men chosen for the mission are Lance Corporal William Schofield (George MacKay), a veteran of the Battle of the Somme, and Lance Corporal Tom Blake (Dean-Charles Chapman), who has an extra incentive as his brother is among the troops readying themselves to go over the top. They are around the same age but differ considerably in their outlook: Schofield, presumably scarred by his experiences in the brutal battle where over a million men lost their lives, is closed off emotionally, while Blake is more plucky and outgoing.
On their perilous journey across the devastated wasteland, Schofield and Blake encounter many dangers: Booby traps, snipers, enemy troops, and a German pilot who fatally stabs Blake after he saves him from a burning plane. Spurred on by his friend’s death, Schofield reaches the front line just as 1600 men are about to charge the German trenches. With only a few minutes to go, can he deliver the message and save hundreds of lives?