"Then Pharaoh called to Moses and said, 'Go, serve the LORD; only let your flocks and your herds be kept back. Let your little ones also go with you.' But Moses said, 'You must also give us sacrifices and burnt offerings, that we may sacrifice to the LORD our God. Our livestock also shall go with us; not a hoof shall be left behind. For we must take some of them to serve the LORD our God, and even we do not know with what we must serve the LORD until we arrive there.' But the LORD hardened Pharaoh's heart, and he would not let them go. Then Pharaoh said to him, 'Get away from me! Take heed to yourself and see my face no more! For in the day you see my face you shall die!' So Moses said, 'You have spoken well. I will never see your face again'" (10:24-29).
The darkness is an intimidating force and Pharaoh calls for Moses and suggests another compromise: All the people may go to serve Jehovah, but all animals must be left here. Moses replied that such was not acceptable. If Pharaoh would not allow them to take their animals with them (i.e., "give" their own animals into their hand), then they could not go. They needed all of their animals since they didn't know exactly what God would require of them. Pharaoh does not take this news well. If all the animals and all the people left, they likely would never return. Pharaoh had no intentions of allowing his slave labor to escape. Pharaoh became so enraged this time that he commanded Moses to not come before him again, if he valued his life.
Moses is not happy either, as the next chapter describes. It is my belief that the dialogue of Exodus 11 was spoken during what was supposed to be the last meeting between Pharaoh and Moses, though the text is not clear on this.