Why is everyone upset when Algernon behavior changes?

Everyone is upset when Algernon's behavior changes because it signifies a decline in his mental capabilities, which reflects the unstable nature of the intelligence-boosting procedure he underwent. Algernon's deterioration highlights the potential risks and ethical concerns associated with artificially enhancing intelligence. His regression serves as a foreshadowing of the protagonist Charlie's own impending decline, creating a sense of anxiety and tragedy among those who care about him. This shift in Algernon's behavior deepens the emotional stakes of the story and raises questions about the value of intelligence versus the essence of being human.