The Lord said to Moses, “Stretch forth your hand toward the heavens, and there will be darkness over the land of Egypt, and the darkness will become darker.” [Exodus 10:21]
G-d wrought 10 plagues upon Egypt. The first three were meant to end the slavery of Israel and make the Egyptians, particularly Pharaoh, uncomfortable. It’s not easy to sip your morning cup of coffee only to taste blood. Or, opening the oven to bake an apple pie only to find dozens of frogs. Or, how about waking up to discover your nose is filled with lice? Ugghhh.
Gradually, the plagues became deadly. The lion growling at your door; your skin covered in boils; hailstones that destroy your front porch and crop. But then came the plague of darkness. What does that achieve except having everybody scramble for a match?
It’s a question asked by some of the commentators in this week’s Torah portion. The answer lies in understanding darkness: It conceals evil. It is also covers for evil people — whether liars, thieves or killers. Darkness also hides intentions. Talk to somebody in the dark and you can’t see his eyes or body language. You rely only on his voice — and he can spin any tale he wants.
But G-d used darkness in another way. It became a means for Israel to shed its last trace of slave mentality before they left Egypt. For decades, the Jews feared the Egyptians, who could beat and kill them at will, abduct their babies and assault their wives. Now, the Egyptians, paralyzed in total darkness, no longer seemed threatening. The Jews entered the homes of their former masters and found gold, jewels and other precious objects. Moses would then command the Jews to return to the Egyptians and borrow their riches. Chutzpah? Yes. Fear? No.
So, Moses stretched forth his hand toward the heavens, and there was thick darkness over the entire land of Egypt for three days. [Exodus 10:22]
All of the plagues represented a miracle. Still, the world has seen many if not all of the plagues. On Dec. 4, 1952, London was plunged into a darkness that nearly exceeded that in ancient Egypt. For five days, a fog so thick it was called pea soup enveloped the British capital. There was no sunlight. People couldn’t even see their feet, let alone each other. Children had to crawl home from school. Cars and buses collided. Two trains rammed into each other on London Bridge.
At night, the fog turned into death. Between 4,000 and 12,000 Londoners died in their sleep from breathing the combination of soot and sulphur oxide that emanated from coal burners in nearly every home in the city.
The British government instituted a policy to stop coal heating. This did not stop the next major pea soup fog in 1962, in which at least 100 died.
Darkness also concealed something else in Egypt: The death of millions of Jews who had assimilated and worshipped the idols of career, money and prestige. The Midrash says these Jews had long left their faith and community. Their lives revolved around their gentile sponsors, who made them rich and prominent. There was no way they would leave Egypt regardless of how many plagues.
During the darkness, all of the assimilated Jews died. The Midrash says the survivors — those who had been persecuted by Pharaoh — exploited the plague to bury the dead. The Egyptians didn’t see a thing.
They did not see each other, and no one rose from his place for three days, but for all the children of Israel there was light in their dwellings. [Exodus 10:23]
But when G-d restored the light, the Egyptians revolted. The young men told Pharaoh that they didn’t want to die fighting the G-d of the Jews. A civil war erupted in which the emperor killed countless young people to survive another day as persecutor.
Still, Pharaoh as well as everybody else in Egypt knew this was the end. He would soon tell the Children of Israel to leave Egypt immediately. He would run screaming in the night looking for Moses and Aaron as the Egyptians died like flies.
There was another utility to the plague of darkness. It became possible to see far away. A modern lighthouse can be detected by boats for nearly 50 kilometers. What the Jews could see in the darkness was their future, settled in the Land of Israel and following a Torah lifestyle. The Egyptians saw nothing.
The Jews have been living in the darkness of Exile for some 2,000 years. Today, it seems darker than ever as the world lurches from one calamity to another. The people seem to have more knowledge than ever, and yet as the commentator Rashi writes in Zechariah, their intelligence is so jumbled that it turns to madness. 
At that point, it takes a Moses or his students to see beyond the darkness. On the eve of World War I, David Cohen, a student of Rabbi Avraham Yitzhak Kook, met the sage and Jewish leader known as the Chafetz Chaim in the Lithuanian city of Radin. Cohen was headed for the Land of Israel. The Chafetz Chaim had tried to move to the holy land but was dissuaded by leading rabbis, who feared that the network of Torah seminaries would collapse in his absence.
The Chafetz Chaim shared a confidence with the young Nazirite, who had sworn off wine and didn’t cut his hair. “At first, I would pray ‘Return in mercy to Jerusalem, Your city, and dwell therein as You have promised’ and thought this was just another prayer. I thought the same when I came to ‘Speedily cause the scion of David Your servant to flourish and increase his power by Your salvation.'”
“But now,” the Chafetz Chaim continued, “when I pray these passages, behold, it seems to me very close. I am old and don’t know whether this will take place in my days. But in your days, it will certainly happen.” 
1. Rashi on Zachariah. 14:13
2. “The Sparks of Light of the Messiah” Rabbi David Cohen. Page 13. Ariel, 1989