The supporting detail from "Night", by Elie Wiesel, that best reflects the key ideas of hopelessness and sadness is "Not cry? We're on the threshold of death. Soon, we shall be inside." Someone hugs the narrator and begins crying. When he tells him not to cry, the other man says that it is impossible not to cry when you are at the door of death and they will soon enter. This shows hopelessness and sadness.
