A team of experts, including historians and archaeologists, embarks on a special expedition in northern France to locate and excavate a secret tunnel used during the Battle of the Somme in 1916. As they navigate the challenges of the excavation, they uncover remnants of the war, including ammunition and personal items, that offer a unique glimpse into the lives of the soldiers who fought in the trenches. The team's efforts to uncover the truth about the secret tunnel and the weapons used in the battle shed new light on one of the most famous and devastating conflicts in history.