In this chapter, Moses releases the plagues of locusts and darkness.
This chapter is very similar to the last. The plagues get worse, Pharaoh continues to buckle and the natural resources of Egypt continue to be destroyed. The plague of locusts is severe, but fairly conventional (with respect to the prior plagues). I find the plague of darkness more interesting, because it afflicts the realm of the heavens, which was populated by the sun.
This is also notable because one of the main Egyptian deities is Ra, the sun god, so the occlusion of the sun is the clearest strike against the Egyptian religious system we have seen yet. This plague also does not strike the land of Goshen, which would suggest it were caused by thick clouds or something. Of course, the text doesn't say what caused the darkness, which indicates that the author doesn't actually care what was the proximate cause. What is more important is the ultimate cause, which is that the plague came as a result of the LORD's judgment of Egypt through the agency of Moses.
Anyway, that's all I have for this chapter. It's basically the same themes as the last two.