Jacob learned that Egypt was selling grain so he sent his sons (except Benjamin, his youngest and only remaining son of his beloved Rachel) to Egypt.
Upon arrival, Jacob recognized his brothers but they did not recognize him -- he spoke through an interpreter so as not to reveal that he spoke Hebrew. The brothers bowed to Jacob, thus completing Jospeph's previous dream that his brothers would all bow to him.
Joseph spoke harshly to them, as the Master of Egypt, and clearly put his brothers on the defensive. He accused them of being spies and put them all in prison for three days until they agreed to send one of them back to retrieve Benjamin so as to confirm the truth of their story -- that they ten were brothers of one family, one of their brothers was back at home in Cannan and the other brother "was no more."
Joseph then called them from prison and told them he would give them enough grain to take home but he would keep one brother in Egypt as a hostage to assure that the other brothers would return with Benjamin. Simeon was bound and put back in prison while the rest of the brothers were given sacks of grain to take back home.
When they arrived back home, they discovered that the sacks contained both the grain and the money (which Joseph had returned). This made the brothers fear that they would be accused of being thieves as well as spies. They told Jacob of the Egyptian Master's demand to return with Benjamin. Jacob balked at this, not wanting to lose his youngest son on such a dangerous mission.