Sunday Sermonette: There must be a lesson in here somewhere

So Joseph's family comes back into the picture in Ch. 42. This is another long one so we'll just do the first half today.

 When Jacob learned that there was grain in Egypt, he said to his sons, “Why do you just keep looking at each other?” ² He continued, “I have heard that there is grain in Egypt. Go down there and buy some for us, so that we may live and not die.”
³ Then ten of Joseph’s brothers went down to buy grain from Egypt. ⁴ But Jacob did not send Benjamin, Joseph’s brother, with the others, because he was afraid that harm might come to him. ⁵ So Israel’s sons were among those who went to buy grain, for there was famine in the land of Canaan also.
⁶ Now Joseph was the governor of the land, the person who sold grain to all its people. So when Joseph’s brothers arrived, they bowed down to him with their faces to the ground. ⁷ 

Note well: Joseph is selling the grain. This was not a humanitarian scheme to save the world from starvation, it was a money-making scheme. Actually it's just outright theft. Joseph never paid the farmers for the grain, he just confiscated it. Now they have to buy it back from him. (As we shall see he does slip the money back to his brothers but everybody else in the world, or what they thought was the world, ends up being dispossessed.)

As soon as Joseph saw his brothers, he recognized them, but he pretended to be a stranger and spoke harshly to them. “Where do you come from?” he asked.
“From the land of Canaan,” they replied, “to buy food.”
⁸ Although Joseph recognized his brothers, they did not recognize him. ⁹ Then he remembered his dreams about them and said to them, “You are spies! You have come to see where our land is unprotected.”

I'm not sure what this means. The only dreams we have been told that Joseph had about his brothers have them bowing down to him. But they're already doing that.

¹⁰ “No, my lord,” they answered. “Your servants have come to buy food. ¹¹ We are all the sons of one man. Your servants are honest men, not spies.”
¹² “No!” he said to them. “You have come to see where our land is unprotected.”
¹³ But they replied, “Your servants were twelve brothers, the sons of one man, who lives in the land of Canaan. The youngest is now with our father, and one is no more.”
¹⁴ Joseph said to them, “It is just as I told you: You are spies! ¹⁵ And this is how you will be tested: As surely as Pharaoh lives, you will not leave this place unless your youngest brother comes here. ¹⁶ Send one of your number to get your brother; the rest of you will be kept in prison, so that your words may be tested to see if you are telling the truth. If you are not, then as surely as Pharaoh lives, you are spies!” ¹⁷ And he put them all in custody for three days.

I don't get the logic of this, do you? How does bringing the younger brother back prove that they aren't spies? 

¹⁸ On the third day, Joseph said to them, “Do this and you will live, for I fear God: ¹⁹ If you are honest men, let one of your brothers stay here in prison, while the rest of you go and take grain back for your starving households. ²⁰ But you must bring your youngest brother to me, so that your words may be verified and that you may not die.” This they proceeded to do.

Not clear why Joseph changed his mind. He was going to send one of them after Benjamin, now he decides to keep one and send nine. Whatever.

²¹ They said to one another, “Surely we are being punished because of our brother. We saw how distressed he was when he pleaded with us for his life, but we would not listen; that’s why this distress has come on us.”
²² Reuben replied, “Didn’t I tell you not to sin against the boy? But you wouldn’t listen! Now we must give an accounting for his blood.” ²³ They did not realize that Joseph could understand them, since he was using an interpreter.
²⁴ He turned away from them and began to weep, but then came back and spoke to them again. He had Simeon taken from them and bound before their eyes.
²⁵ Joseph gave orders to fill their bags with grain, to put each man’s silver back in his sack, and to give them provisions for their journey. After this was done for them, ²⁶ they loaded their grain on their donkeys and left.

Joseph is messing with their minds, evidently. We'll see how it turns out anon. Meanwhile, looking ahead, God is working in mysterious ways. The first consequence of this plot is to put all the money in the world into Joseph's hands. The next consequence will be the Egyptian captivity.