As the group heads down the tunnel, the sound of metal on stone gets clearer and clearer. The area also gets progressively darker, and those without darkvision are soon squinting. Planus's ears are sharpest, and he slows the group, indicating that he believes that miners are working not far around the corner -- the sounds seem to be about 40' away. The group faces a dilemma: beyond the next corner it's pitch dark, but a light would certainly give away any surprise that might otherwise be obtained.