You decide to check out the door before you see if there are any footprints leading into the tunnel. As you grab the handle you can feel it's warm to the touch. As the door swings open, you are blasted with heat and smoke from the burning hallway. You gag on the smoke and stench of the burning bodies and basement structures. Quickly, you slam the door shut and call out to the other prisoners that are still on the other side of the wall in the burned out lab. "Hurry, climb over the wall. Your only way out is through the ceiling. There's too much fire and smoke to go back to the hallway." The prisoners hear you and scramble over the wall to where you are. There are now three prisoners with you trapped in this small hallway. The only direction you can go now is through the dark tunnel. Unfortunately, you don't have your sack with you anymore with all the items you gathered in your travels. That means you no longer have your flashlight. How are you going to get through the tunnel?
The doorway is facing the wrong way to allow light to enter the tunnel. You had to leave you sack behind in the prison cell hallway so you could carry your weapons and fight any battles you faced. You could try to run back and retrive the flashlight but you will probably be overcome by the smoke. There must be another way.