In the novel Night, what happens at the end of the book?

In the end of Night, Elie and his weakened father arrive at Buchenwald after enduring a forced march and a death-train transport. In the train, food was thrown into the cars by people in the passing villages who then watched as the starving prisoners fought and killed each other to get food. Dead bodies, whether dead from starvation or illness or agedness, were thrown out of the train cars by guards, bodies left in a naked, untended condition by the rail tracks.

With this experience behind them, and now imprisoned in a new camp, Elie's father, although Elie forces him to continue trying, becomes deathly ill. Elie arranges to stay in the same cell block with his father--and when his father cried for water, while Elie hesitated because of his father's dysentery, a guard beat his father in the head. On the last night of his life, while Elie slept unsoundly above him, Elie heard his father call his name once. In the morning, someone else was in his father's bed. He had cried out when they came to take him to the death chamber, the crematory. Stunned and numbed by his grief and by his release into freedom (he is by himself now and can concentrate his thoughts and efforts on his own survival, "free at last!"), he is uncaring when transferred to the children's block.

One day the Nazis announce their plan to assemble the prisoners, evacuate them (the prisoners forming the resistance thought "evacuate" meant a final, total extermination), then blow up the camp. The plan was formed because the Germans were losing the war and the Allies were advancing, liberating all those suffering from the prolonged, horrible war. On the day announced, because of a delay caused by a siren alert, the call for all prisoners to assemble was moved to the next day. Next day when assembly was called, one member of the resistance movement told Elie and the other young ones to retreat and hide in the children's block. Once all were assembled, the resistance members turned on the Nazi soldiers. They defeated them fairly easily because the soldiers no longer had the will to be there nor to shed their blood there. Later that same day, the miracle that no one believed in any more happened: the first American tank rolled up to the guard-abandoned gate of the camp. The prisoners were liberated and fed.

   Hunger was tormenting us; we had not eaten for nearly six days....   
... At six o'clock that afternoon, the first American tank stood at the gates of Buchenwald.
   Our first act as free men was to throw ourselves onto the provisions....

In another cruel act of an unloving fate, Elie developed a life-threatening case of food poisoning (food, the thing he dreamed about and clung to the hope of after his father's death nearly killed him) and, while being treated in the hospital, chose to look at his reflection for the first time since the Nazis had rounded him and his fellow Jews up to kill or use as slaves. What he saw in the mirror became seared in his mind's eye. Changed beyond recognition, Elie saw a living corpse staring back at him. Still, his consolation was that night had ended. Day might now come.

    And now the boy is turning to me. "Tell me," he asks, "what have you done with my future, what have you done with your life?" And I tell him that I have tried. That I have tried to keep memory alive, that I have tried to fight those who would forget. Because is we forget, we are guilty, we are accomplices. (from The Nobel Peace Prize Acceptance Speech delivered by Elie Wiesel, appended in Night)