In Elie Wiesel's Night, we see the author go through significant and life-altering changes as he faces horrific situations and conditions in the German concentration camps of the 1940s—on physical, emotional and spiritual levels.

Elie is quite young when his family is separated: the women are sent to the gas chamber, and Elie and his father fight to survive as they are put to work at Auschwitz-Birkenau.

When the story starts, Elie is extremely spiritual. He loves learning about the faith of his Jewish ancestors, and spends a great deal of time with Moshe the Beadle who instructs him in "the mystical side of Hasidism." 

Moshe the Beadle, the poor barefoot of Sighet, talked to me for long hours of the revelations and mysteries of the cabbala.

Elie's faith was a significant part of his being, of his heart.

He watched me one day as I prayed at dusk. “Why do you cry when you pray?” he asked… “I don’t know,” I answered… “Why do you pray?” he asked after a moment. Why did I pray? Strange question. Why did I live? Why did I breathe?

However, by the end of the novel, Elie questions God. Whereas Elie had enjoyed a strong relationship with God before the Nazis took his family, as the days go by at the camp and each day brings renewed suffering, horror and despair, Elie no longer looks to God for answers. Instead, he breaks with God and, as he sees it, accuses God. He recalls the relationship between God and His creations: God exiled Adam and Eve from the garden; He brought the flood during Noah’s day to punish sinners; and he destroyed Sodom and Gomorrah for the behavior of the cities' citizens. In the concentration camp, Elie questions why God was punishing the men of faith around him, and stands amazed that their faith is undiminished:

…look at these men whom You have betrayed, allowing them to be tortured, slaughtered, and burned, what do they do? They pray before You! They praise Your name!

Elie struggles to rediscover his once-strong faith in God as he sees the men around him ever turning to God and praising Him, despite their devastating circumstances. Elie notes:

Never shall I forget those moments which murdered my God and my Soul and turned my dreams to dust.

Elie is young and healthy at the story's beginning. He has so much of life before him. However, by the end of the story when the Allies liberate him and the rest of the camp, he tries to adjust to being free, clean and fed. It is all very difficult for him, having faced daily the real possibility of his own imminent death and watched his father die day by day—even while the older man tried to protect his son. When Elie looks in the mirror, the image he sees is nothing like the young man he was when his account begins. By the end, he has life, but his reflection does not describe someone who is alive:

From the depths of the mirror, a corpse gazed back at me. The look in his eyes, as they stared into mine, has never left me.

In terms of the emotional changes Elie faces, one of the most difficult to see is Elie's deteriorating relationship with his father, Chlomo. Elie's father had always watched over him and continues to do so at the camp as best as he is able. It is not long after Elie and his father arrive at the first camp that the reader can anticipate the changes that will take place between father and son. When Chlomo asks to use the restroom when they are brought into the camp, a guard strikes Chlomo extremely hard:

I did not move. What had happened to me? My father had just been struck, before my very eyes, and I had not flickered an eyelid. I had looked on and said nothing.

Toward the end of the story, Elie and Chlomo are "shipped to Gleiwitz, and then taken to Buchenwald." These trips are grueling beyond imagination—running for hours in the snow without proper clothing, food or shelter. Elie's father becomes sick. As Chlomo's health further deteriorates and while Elie is himself struggling to survive, Elie must take on the responsibility of caring for his father, trying desperately to keep him awake and moving so the guards don't leave him behind or kill him. Before long, as his father becomes slower to respond, Elie begins to resent the older man more and more—feeling guilty even as he does so. When his father dies, Elie is unable to cry:

Then my father made a ratline noise and it was my name: ‘Eliezer…’ I did not move…His last word was my name…I did not weep, and it pained me that I could not weep. But I had no more tears. And, in the depths of my being, in the recesses of my weakened conscience, could I have searched it, I might perhaps have found something like—free at last.

Central to the story are the intertwined themes of health and change: the change of Elie's physical appearance and strength, Elie's spiritual loss, and the ravaging toll his experiences take on him emotionally. It is little wonder that by the end of the story Elie feels like one who is almost dead—especially with regard to these three areas of his life.

At the very end of Night, Wiesel states that he looks into a mirror for the first time since being imprisoned. He writes,

“From the depths of the mirror, a corpse gazed back at me. The lookin his eyes, as they stared into mine, has never left me.”

These finishing lines present the idea that the experience has, in a sense, “killed” Wiesel.

This death is primarily spiritual. Before his imprisonment, Wiesel, as a teenager, lived for his spiritual beliefs. His only goal for the future was to become more and more involved in the higher aspects of Judaism. During his time in the concentration camps he ceases to feel this way. He also denounces his own faith in the good in people, in the sense that he no longer believes in his ultimate mercy, although he still believes in God’s existence.

In the book Night, often readers assume that Elie has lost his faith in God completely.  In reality, Elie feels a bit like Job, a person in the Bible who questioned God and was put through many trials just like Elie. Elie is angry with God, tired of God's silence in the hell he lives in, angry with the world which ignores what is happening to him, but in the end, still keeps his faith that there is a God.  Elie explains in his own words, "I did not deny God's existence, but I doubted his absolute justice." In light of the narrative Night, his feelings are illuminated and understandable.