Menahem Mendel Beilis was a man who lived a long time ago in a place called Russia. He was a Jewish man who worked as a clerk in a factory. In those days, some people didn't like Jewish people very much and they would say mean things about them.
One day, a boy who worked in the same factory as Menahem Mendel was found dead. Some people thought that Menahem Mendel had killed the boy because he was Jewish and they didn't like Jewish people.
Menahem Mendel was put on trial, which means that he had to go to court and try to prove that he didn't do anything wrong. A lot of people didn't believe him because they thought that all Jewish people were bad.
But Menahem Mendel's lawyers were very smart and they worked very hard to prove that he was innocent. They showed that the boy had not been killed by Menahem Mendel, but instead there was a group of bad guys who had killed him for a different reason.
In the end, Menahem Mendel was found innocent and was able to go back home to his family. This story taught us that it's important to treat people fairly and not to believe bad things about them just because of who they are.