The brothers were all set to leave the next morning, to take the grain from Egypt back to their home.
Joseph told his steward to fill their sacks with grain and silver, and also to put his super-special divining cup in Benjamin's sack tee-hee-hee. What a good joke. Fill those miscreants with terror just one last time.
Then the brothers set off on the road home, probably with a big 'whew!' before they saw Joseph's steward running toward them, shouting.
The steward told them that they had obviously made off with his master's special divination chalice, made of silver, and that it was a naughty thing they'd done indeed.
The brothers protested, not remembering having stolen anything, and they told the steward that if he could find the cup in their bags, the owner of the bag would have to be put to death and the rest of them would become slaves.
The steward told them that was a bit drastic: the person who took the cup would become a slave, but the rest of them could go free.
Then the steward found the cup in Benjamin's bag. Doh!
Now, this would be a pretty good joke if I didn't imagine the brothers' faces going completely white at the sight of the cup. They're bastards, but I have to sort of feel sorry for them. They were obviously being tortured at this point.
They all trundled back to the city and threw themselves at Joseph's feet.
Joseph scolded them for taking the cup, saying, didn't you know I could divine things? I suppose he meant even without his super-special divination cup.
The brothers told him they were all his slaves now.
Joseph told them to go home, only the one that took the cup was to be his slave.
I'm sure the brothers felt staying in Egypt as a slave was going to be better than what awaited them at home. Judah tried to intercede.
Judah explained, tediously, the entire story to Joseph, including the things Joseph himself had said. Judah told Joseph that it was hard to part Benjamin from his father because of their attachment, and that if they returned without Benjamin, their father would surely die.
Because Judah was the one that vouched to his father for Benjamin's safety, he asked Joseph to take him as a slave instead of his brother.
This is a rather noble thing, I must say. Good job, Judah.