Passage: I was lying down in a dark, lonely compartment of the speeding train, trying to sleep. But, quite unusually, sleep eluded me. A vague uneasiness gripped me. It was pitch dark outside. A few points of light flashed by as we sped through a small station and in the dim light I thought I saw a hand gripping the bars of my window. Once again the train was swallowed up by the impenetrable darkness. My heart pounded. My mouth was parched. I could not get up. I do not know how long I remained thus before the train began to slow down. The reassuring bright lights of the station we were entering revealed no intruder. I breathed again. Question: The narrator could not sleep because