"The Mysterious Stranger" is a novella written by Mark Twain, published posthumously in 1916. The story follows a young boy named Augustus, who encounters a stranger with supernatural abilities. This stranger challenges Augustus's understanding of free will, morality, and the nature of existence. The narrative is set in 19th-century Europe and explores philosophical themes, including determinism and the illusion of choice. The stranger reveals that life is a mere illusion, leading Augustus to question the meaning of his own life and the world around him. The work reflects Twain's critical views on society and human nature.