The Pathless on Paths---------Chapter VI part 3(12)

The group headed for a staircase on the other side of Sector U, to the west. With each step the Geiger counter built into Karrson’s gas mask crackled more furiously, being nearer to the rent in the wall, and as a more remote area, the number of infecteds fell. The corridors they now walked had little illumination and were strangely dim, as if the walls absorbed light. They kept going for sometime, unhindered.
Suddenly, Clark at the front of the company slipped and fell, sliding on the floor.