They found the first gap in the ridge system on the fourth day.
It was not dramatic — a narrowing in the channel that opened sideways, a natural break in the left ridge wall wide enough for two people to pass through comfortably, leading into a space beyond that was lower and more open, a broad shelf of ground between two ridge formations that created something almost like a valley. The floor was flat and the bonedust here was undisturbed in long stretches, which meant nothing had been through it recently — or nothing that left tracks in the way living things leave tracks.
They made camp on the shelf that night.
