In 1918, in the Western Front in France, Lt. Berton, a Canadian tunneler, digs 78 feet beneath a German position to rescue other tunnelers. Berton accidentally startles a survivor who ends up screaming, alerting the Germans above. The Germans then detonate charges above Berton, trapping him underground for twelve days.Three months later, in November 2, 1918, a pair of British Army intelligence officers, Maj. Jennings and Dr. Priest, debrief Col. Ashcroft with intelligence information on a deep underground German bunker called "Trench 11", hidden within the Argonne Forest. The base is commanded by a German officer named Reiner (who is called "The Prophet" by his men) who specializes in weaponizing various chemicals and diseases. Jennings and Dr. Priest believe that Trench 11 (so named because it is eleven miles behind German lines) is used as a base of operations for Reiner to make more weapons and request for the bunker to be investigated as the Germans failed to destroy it during their retreat. The colonel arranges an American escort (due to the fact that the Argonne Forest is within their sector of the front) and allows Jennings to retrieve Lt. Berton from his leave to help with their investigation. During his leave, Berton enters in a romantic relationship with a French woman named Veronique but is forced to leave when he is retrieved to aid Maj. Jennings' investigation.Berton accompanies Maj. Jennings and Dr. Priest to Trench 11 along with their American escorts: Capt. Cooper, Sgt. Pronger, and Pvt. Kelly. Upon locating Trench 11, the group discover dead German soldiers in the trenches. It is revealed that the German Army had shelled Trench 11 prior to the Allied soldiers arriving there.At the headquarters of the German 5th Army, Gen. Ophuls orders Reiner and Capt. Mueller to erase all evidence of the nature of Trench 11 (called "Wotan Complex" in German) to prevent the allies from discovering it as Reiner failed to detonate the explosives inside during their retreat. Mueller, who is disgusted by Reiner's work, is ordered to escort Reiner to the bunker to get the job done.In the trench, the group discover evidence of German infighting and sabotages. Descending underground they come upon a sealed door and a German soldier who was left behind. The soldier frantically begs the group not to open the door but Jennings orders his men to ignore him. The German soldier then hysterically begs and pressures Cooper into shooting him. The group moves deeper into the bunker and are attacked by a crazed man who vomits on Kelly and rips a grenade off Pronger. Berton tosses the grenade away but collapses the tunnel they came from. Jennings orders Berton and Cooper to split and search for an exit while he, Dr. Priest, Pronger and Kelly investigate further down.While searching for an exit Berton and Cooper are ambushed by more crazed men. Cooper is stabbed by one and both are forced to fight them off and flee. Simultaneously Jennings, Priest, Pronger and Kelly discover a hospital room. Pronger is attacked by a crazed man but manages to kill him, alerting the group to a worm crawling out of the gunshot wound. Dr. Priests performs an autopsy on the deceased man and discover the man's body is full of worms and is responsible for his insane and violent behavior. Dr. Priests concludes the worms are not natural and were engineered. Pronger and Kelly stage a mutiny and demand they leave the bunker which ensues a standoff between them and Jennings. The group is then ambushed by German soldiers who kill Pronger and Jennings and take Kelly and Dr. Priest prisoner. Berton and Cooper discover an exit but are also taken prisoner.After losing his tunneler to the infected (whom they needed to reactivate the charges), Mueller decides to recruit the group but Dr. Priest refuses to cooperate. Reiner, who was eavesdropping the whole time, singles out Dr. Priest for interrogation. Kelly's health deteriorates and becomes sick.Reiner interrogates Dr. Priest and tries to get him to relate to his twisted view on science. Dr. Priest figures out the worms were meant to kill allied livestock but jumped species to infect humans. In turn, Reiner reveals that he marveled at the results and deliberately bred deadlier strains. Mueller escorts Berton, Cooper and Kelly into the lower levels where the charges is located but Kelly succumbs to the parasite and kills Cooper. Berton shoots Kelly and holds Mueller at gunpoint, but stands down after Mueller convinces him that the parasite will kill everyone if it ever gets out. Dr. Priest desperately tries to reason with Reiner not to use parasite for the sake of civilian lives, but Reiner remains adamant in using the parasite to destroy Europe and rebuild it under German rule. He then tortures Dr. Priest.Mueller and Berton locate the charges and learn that the explosives were never rigged in the first place. After killing Dr. Priest, Reiner orders his men to seal the lower level and flood it with poison gas and begins to collect his parasites. Mueller and Berton are forced to flee and find another way to detonate the explosives. Berton tries to rig the explosive to a clock timer for a remote detonation but an infected soldier attacks them, breaking Mueller's leg and destroying the clock. Unable to move, Mueller stays behind and gives Berton time to arm any remaining explosives and escape. Berton finishes and reaches for the exit, but is shot in the leg by Reiner and his guard. Reiner then mocks and tortures Berton, who endures it to distract Reiner and his guard long enough for Mueller to detonate the explosives. The explosion catches both of them off guard, which allows Berton to kill the guard and engage Reiner in a brawl. Reiner attempts to flee but Berton trips him; resulting in his eye being impaled by a vial in his hand. The tunnel collapses on Reiner while Berton barely escapes. Berton limps away from the site and sees a vision of his lover Veronique; his ultimate fate is left ambiguous.(copied from Wikipedia)