Set during World War I, a group of British soldiers "go over the top" in an assault against German lines. However, in the middle of the battle, a mysterious fog descends upon the battlefield and the night suddenly turns into day. Hours later, they finally stumble upon the German trenches only to find a mere 3 German soldiers, petrified and pointing their guns down their own trenches. The British soldiers call for them to surrender, but the Germans are more scared of something in the trench than them. After murdering two of them and torturing the third, the British troops begin exploring the trench, only to find the bodies of more Germans, seemingly killed by friendly fire. Even stranger, the trenches seem to lead nowhere, simply doubling back on themselves. With a prisoner babbling about demons, impenetrable fog, and a broken radio, they quickly form a defensive position and wait for reinforcements that never come.
Though their radio can't send messages, it can still receive them. High command seems rather sure that the attack failed and there were no survivors....
Needless to say, things go downhill from there.
This movie provides examples of:
- Anachronism Stew: Not very overt, but there are some inconsistencies, especially with the weapons. The Lee-Enfield rifles wielded by the soldiers are WWII-era variants of the rifle (the WWI rifle being harder to come by at this time). But the most obvious example by far is the surprisingly small radio receiver they find and repair. No country had military or civilian radios that small and advanced during WWI. It would fit better in the 1920s. In addition, most of the German rifles are actually WWII-era Kar98k's, instead of the Gewehr 98s they should have been using.
- Ax-Crazy: Quinn.
- Before he even goes over the top, he's taunting the Germans and grinning at the prospect of battle.
- He taunts an enemy soldier before shooting him and attempting to scalp him. Just what is that fur coat of his made of, anyway?
- In his final scene, he attempts to crucify Friedrich while screaming into the abyss for the Germans to come and kill him. He then brutally stabs Jennings and bludgeons Tate.
- Captain Smooth and Sergeant Rough: Jennings and Tate fit this, but it's subverted by Tate being somewhat more sympathetic than Jennings.
- Cruel and Unusual Death: Plenty of examples:
- Starinski is attacked by a dead soldier and later found wrapped in barbed wire.
- McNess is pulled into the ground by...something.
- Quinn is attacked by moving barbed wire, and is impossibly still alive after being penetrated through the neck and face multiple times. Charlie is forced to shoot him.
- Doomed Hurt Guy: Chevasse spends the majority of the film on a stretcher, paralysed from the neck down. Towards the end of the film, Charlie discovers that while everyone has been distracted by the horror going on around them, the still-conscious Chevasse has been partially eaten alive by rats.
- Eldritch Location: Wherever the squad have gone, it's taken a match to the rule book of physics; trenches seem to reappear after being blown up, there are strange noises in the fog, and blood pours from the mud after one explosion.
- This goes double for the space under the trench that Shakespeare finds himself sucked into at the end of the film.
- Fog of Doom: Hey, it's World War I. Fog of Doom is already all over the damn place, both natural and weaponized.
- Foreshadowing: Many of the characters seem to meet their death in a similar position to the one they were left in during the opening scene.
- Tate gets caught on barbed wire during the opening scene, and later gets thrown into barbed wire and trapped before he's bludgeoned by Quinn.
- Karmic Death: Most of the cast, who are each shown to be morally flawed (or just unlucky) in some way, are shown to get their comeuppance in various gruesome ways. Especially Quinn.
- Last-Name Basis: A subversion, since in the script and credits, the characters are mentioned by their full names. But the only personal name used on screen regularly is Charlie's.
- Let's Split Up, Gang!: Despite blowing up the approaches to their trench to limit the space they have to defend, the squad never seem to be within sight, earshot, or running distance of each other when anything happens, and stationary, presumably vulnerable characters like Chevasse and the prisoner go unguarded and unmentioned for long stretches of the film. Unsurprisingly, this results in a Dwindling Party.
- Maybe Magic, Maybe Mundane: Many of the events in the movie could be put down to the soldiers being driven mad on some kind of gas, and (some of) the deaths themselves are grounded enough that the events leading up to them could be written off as hallucinations, or explained in some other way.
- Mercy Kill: Charlie does this to Chevasse after he discovers rats are eating his legs.
- Arguably Quinn, since the barbed wire doesn't kill him, and Charlie has to shoot him.
- Nothing Is Scarier: The earlier portions of the movie, before the squad members start getting killed off in mysterious ways.
- Officer and a Gentleman: Averted by Jennings and Tate, both of them enormous JerkAsses.
- One-Word Title
- Only Sane Man: Charlie provides a consistent voice of reason, and often tries to mitigate brawls between the other characters as they slip into madness. Besides Charlie, McNess has the firmest grasp on the Sanity Ball, as the only one who voices the opinion that they really, really need to leave.
- Our Ghosts Are Different: They might be hallucinations.
- Psychotic Smirk: Quinn most of the time. By the end of the movie, Bradford has an even creepier smile on his face when threatening Charlie.
- Sanity Slippage: All the characters, with the possible exceptions of Doc and Chevasse.
- Secret Test of Character: Charlie's persistent and mounting refusal to kill anyone seems to be what separates him from his squadmates until he does, is apparently sucked into the underworld, escapes, is then held at gunpoint by the prisoner, and is released... Because You Were Nice to Me.
- Sinister Minister: Bradford slowly morphs into this because of his gradual Sanity Slippage. He was quite The Fundamentalist before as well, just not insane yet.
- Sliding Scale of Idealism Versus Cynicism: Unabashedly cynical in it's portrayal of The Squad, whose members are mostly bastards at best and violent psychos at worst. Needless to say, the image of the tragic yet cheerful "Tommies" seen in British World War I propaganda gets completely shattered...
- Sociopathic Soldier: Quinn."Thank god he's on our side, eh?"
Quinn: "I went to Blackpool once..."
- How about this exchange ?
Starinski: "Oh, was it nice ?"
Quinn: "I killed a man there... Yeah, it was nice."
- Stripped to the Bone: The rats infesting the trenches somehow manage to pick the flesh and muscle from the oblivious, paralysed Chevasse's legs without him bleeding to death in the process.
- Swarm of Rats: True to life, the trenches are full of rats.