The Jewish people are commanded to take a sheep on the 10th of the month and guard it until the 14th. The sheep is then to be slaughtered as a Pesach offering, its blood put on their door-posts, and its roasted meat eaten. The Jewish People are told to memorialize this day as the Exodus from Egypt by never eating chametz on Pesach. Moshe relays Hashem's commands, and the Jewish People fulfill them flawlessly. Hashem sends the final plague, killing the first born, and Pharaoh sends the Jews out of Egypt.
Nothing is more frightening than nothingness.
Maybe it's something much more fundamental that frightens us. Even when we grow to adulthood, we never quite lose our fear of the dark. If we no longer fear it as we did when we were children, it's because we have the means to restore the light. We know we can get out of bed and flick the switch. We're in control.