One thing we can say for sure about God: He doesn’t leave us in the dark. If we eventually find ourselves in darkness, it’s because we have put ourselves there and have chosen to stay there.
In the story of The Plagues, things start out with Pharaoh’s "magicians" able to replicate the signs and wonders that Moses and Aaron are performing in the name of the Lord. Thus, we might argue that Pharaoh has little motivation to believe that Moses and Aaron are actually representing any god worth listening to.
During the second plague, however, even though the magicians are able to also "make frogs come up on the land" of Egypt, God has a special trick up His sleeve. Moses tells Pharaoh that he will announce the time that the plague will come to an end. This increases "the light" for Pharaoh just a little bit. He has the opportunity to see that these frogs aren’t just some sort of coincidence.
By the time we get to the third plague, the magicians are unable to replicate it. Thus, they tell Pharaoh plainly, "This is the finger of God." (vs 19) How’s that for increased light? That’s like a 2×4 of light whacked over Pharaoh’s head. They understand what’s going on, but Pharaoh’s not ready to buy in just yet.
For His next revelation to Pharaoh, God sends a plague of swarming flies. But this time, just to make sure there are no questions in Pharaoh’s mind about where the plague came from or what the motives are, God restricts the flies to the houses of the Egyptians. There is not a single fly to be found in the land of Goshen where the Israelites lived.
Certainly, by this time, Pharaoh has to be sensible of what’s going on. He actually agrees to let the Israelites go off into the desert to make sacrifices to God, as long as they don’t "go very far." (vs 28) But once the flies are removed, Pharaoh changes his mind. What’s in play now? Pride? Annoyance? Maybe Pharaoh doesn’t like meeting a God he can’t control...
Regardless, it’s fascinating to me to see the way God is communicating something new with each plague. From the inability of the magicians to replicate it, to letting Pharaoh dictate the time it will cease, to restricting a plague so that it only hits the Egyptians... God is slowly letting Pharaoh know that, indeed, He is the one true God. He is always increasing His light in our lives!