The book tells the story of Tom Sawyer, a young boy growing up in the American town of St. Petersburg, Missouri, in the mid-19th century. Tom gets into a lot of trouble, both with the authorities and with his Aunt Polly. But he also has a lot of adventures, both good and bad. He goes swimming in the Mississippi River, gets lost in a cave, and runs away from home. He also witnesses a murder, and helps to solve the crime.