Forget the locusts. And the darkness.
It is not until the tenth and final plague, the death of the first-born--"...from the first-born of Pharaoh who sits on his throne to the first-born of the slave girl who is behind the millstones; and all the first born of the cattle"--that Pharaoh finally gets the message.
"'Up, depart from among my people,'" he thunders at Moses and Aaron, whom he summons in the middle of that deadly night. "'You, and the Israelites with you!"
Meanwhile, the Israelites are given in advance very specific instructions by G-d (through Moses) of how to prepare for that terrifying moment. They are to sacrifice lambs "without blemish...(take) some of the blood and (put) it on the two doorposts and the lintel of the houses in which (you) are to eat it." They are to "'...eat it hurriedly: it is a passover sacrifice to the lord..And the blood on the houses where you are staying shall be a sign for you: when I see the blood I will pass over you, so that no plague will destroy you when I strike the land of Egypt.'"
The chronology within Bo is complicated. First, G-d announces the establishment of the Jewish calendar, for until their freedom, the Israelites have no control over their time. The night in question corresponds with the 15th of Nisan, "'the first of the months of the year for you'". But before any of this has even happened, G-d is already demanding that the still-enslaved Israelites remember this future moment of redemption "'throughout the ages; you shall celebrate it as an institution for all time.'"
"'...For on this very day I brought your ranks out of the land of Egypt,'" G-d says. "'...You shall eat unleavened bread until the twenty-first day of the month at evening. No leaven shall be found in your houses for seven days. For whoever eats what is leavened, that person shall be cut off from the community of Israel...'"
In the dramatic narrative that follows, the "six hundred thousand men on foot" (in addition to women, children, livestock and a "mixed multitude") flee Egypt so quickly that they take with them "baked unleavened cakes" whose dough had no time to rise.
Bo continues with a description of rituals including the symbolic consecration of the first-born ("'the first issue of every womb among the Israelites is Mine'") and the wearing of t'fillin during prayer, giving those who wrap themselves in these leather straps each day a powerful physical and spiritual reminder of the Biblical moment that changed the lives of the Jewish people forever, ultimately leading us to the land of Israel, where we continue to live until this day.
"'And this shall serve you as a sign on your hand and as a reminder on your forehead--in order that the Teaching of the Lord may be in your mouth--that with a mighty hand the Lord freed you from Egypt.'"