Rudolf Abel was a man who lived a long time ago and he was a spy. A spy is someone who works for a country but tries to keep it a secret from other countries. Rudolf was born in Russia but he moved to different countries to do spying work. He lived in the United States for a while and did a lot of sneaky things to try and learn secrets for his country.
But one day, the United States people found out about what Rudolf was doing and they arrested him. Arrested means when the police take you away because you did something wrong. The United States people put Rudolf on trial which means they asked him questions about what he had done and why he did it. The trial was very big and a lot of people heard about it.
Rudolf was found guilty, meaning he did something wrong, and was sent to prison. Prison is a place where people go if they do something wrong and need to be punished. But even though Rudolf was in prison, his country did not forget about him. They kept trying to get him back, almost like when you lose your favorite toy and keep looking for it.
Finally, the United States and Rudolf's country agreed to exchange him for another person. It is like when you have two toys that you and your friend want to trade. Rudolf was sent back to his country and he lived there until he died. Some people think Rudolf was a very good spy because he was never caught before, but other people think it is wrong to spy because it is sneaky and not honest.