Gravity Battlefield: Lens Hunt

At an altitude of 5,300 meters, seven border guards were ambushed by invisible enemies. They all died and no one survived. Everyone said it was an accident. I was the only one staring at the gravity data returned by the satellite - a ten-kilometer-long cross-border tunnel 20 meters underground, crawling like a poisonous snake toward the war-ready oil depot deep inside the national border. My name is Ling Ce, a retired pilot. I injured a leg, but I have a pair of eyes that can see through the ground. Do the enemies think they are safe hiding underground? I will let them know that in front of the gravitational lens, there is no dirt that cannot be dug through, only the truth that cannot be hidden.