"'I will harden Pharaoh's heart," G-d informs 80-year-old Moses and his 83-year-old brother Aaron, "'...that I may multiply My signs and marvels in the land of Egypt. When Pharaoh does not heed you, I will lay My hand upon Egypt and deliver My ranks, My people the Israelites, from the land of Egypt with extraordinary chastisements. And the Egyptians shall know that I am the Lord, when I stretch out My hand over Egypt and bring out the Israelites from their midst."
In other words, it's time for the 10 plagues.
At first, Pharaoh refuses to get the message, commanding his "wise men and sorcerers" to prove that they, like Aaron, can turn their rods into a serpent (though "Aaron's rod swallowed their rods"). G-d instructs Moses and Aaron to confront Pharaoh "in the morning, as he is coming out" of the Nile and for Aaron to "hold out your arm over the waters of Egypt...that they may turn to blood". Seven days later, G-d gives the brothers another script: "'Say to (Pharaoh), 'Thus says the Lord: Let My people go that they may worship Me. If you refuse to let them go, then I will plague your whole country with frogs.'" (See photo, though this frog is menacing Central Park.)
According to the Passover ditty popular in Jewish pre-schools around the world, "frogs were jumping everywhere, even in Pharaoh's underwear!" That could explain why Pharaoh finally gives in, agreeing to let the Israelites "go to sacrifice to the Lord." Not! "When Pharaoh saw that there was relief, he became stubborn and would not heed them, as the Lord had spoken."
So next came the lice (as my family well knows, my personal bugaboo, pun fully intended). But even that doesn't work since "Pharaoh's heart stiffened"; after agreeing to let the Israelites travel a distance of three days to make sacrifices and worship G-d, Pharaoh again change his mind when G-d removes the lice and swarming insects at Moses's urging.
While the Israelites also suffer from the first three plagues, G-d then "(sets) apart the region of Goshen, where My people dwell" so that they will be safe from the rest. But back to the plagues. Wild animals don't work. Neither does the pestilence that kills the Egyptian livestock. Nor the "inflammation breaking out in boils on man and beast". At first it seems like the hail does the trick since it was "very heavy--fire flashing in the midst of the hail--such as had not fallen on the land of Egypt since it had become a nation." And Pharaoh, begging for mercy at last, tells the brothers "'I stand guilty this time. The Lord is in the right, and I and my people are in the wrong...I will let you go; you need stay no longer.'"
Not! As soon as Moses "spread out his hands to the Lord: the thunder and the hail ceased...So Pharaoh's heart stiffened and he would not let the Israelites go, just as the Lord had foretold through Moses." Wait until Pharaoh sees what's coming next week!