What does it refer to in the sentence? I woke for my shift as the sun set into a wadi. It snaked off beyond the orchard, cut into the foothills and disappeared. The fires in the orchard had gone out, but Murph and I did not notice their absence until we heard the thin crackling of embers gently smoldering in the distance. The shadows of the outbuildings reached down and covered everything and we didn’t notice it was happening and then it was night. What does it refer to in "we didn't notice it was happening"? Thanks!