As was mentioned in the previous post, an inspector of the Hungarian police knocks on Elie's window to warn his family that they are in danger. In Chapter 1, the Jews living in Sighet are forced to occupy two ghettos throughout the town. While they are living in the ghettos, the Jewish citizens are unsure of their fate. Elie's father is a prominent figure in the community and is friends with an inspector of the Hungarian police. The inspector had promised Elie's father that he would knock on their window if they were in danger. Before the Jews were rounded up into cattle cars and taken away to concentration camps, the inspector knocks on Elie's window. Unfortunately, by the time Elie's family has the chance to open the window, the inspector has vanished, and they did not receive his message about the impending transports.
A passage on page fourteen of Elie Wiesel's Night states why someone was knocking on the window of Elie's family home. The Jewish people of Sighet had been told to pack because liquidations would begin the following day. Elie and his family had just heard the news and were speaking about what they thought was to come. At one point, they heard a knock at the window. At the time of the knock, the Wiesel family did not know why someone was at their window. As they later found out, the person at the window was a friend of Elie's father (and a member of the Hungarian police). He had told Elie's family that if he had news of something bad happening that he would warn them. The knock at the window was the man's warning. Since they had waited too long to open the window, the man was gone and so was the warning.