They are being hit with mustard gas, which burns the lungs and will kill them very slowly if they breathe it. A few feet away, a new recruit is on the ground. Paul crawls to him, pulls his gas mask on, and then jumps back into the shell-hole. Kat, Kropp, and another man take cover there as well. They can barely see through the goggles of their gas masks.
Gas starts collecting in the hole, but they are trapped by the shelling.
A shell hits the ground and sends a coffin flying on top of them. It hits the fourth man and traps his arm. They free him and use wood from the coffin to make a splint for his broken arm. The gas masks are suffocating. The shelling stops, and Paul crawls out of the hole.