Given the question: Generate a question that has the following answer: Four for the following movie plot: The film is structured around lengthy flashbacks as the elderly Charlie Chaplin (now living in Switzerland) recollects moments from his life during a conversation with fictional character George Hayden, the editor of his autobiography. Chaplin's recollections begin with his childhood of extreme poverty from which he escapes by immersing himself in the world of the London music halls. After his mother Hannah Chaplin has an attack of nerves on stage during a performance, the four year old Chaplin takes his mother's place on the stage. Hannah retires from performing and is eventually committed to an asylum after developing psychosis. In the years that follow Chaplin and his brother Sydney gain work with variety show producer Fred Karno, where Chaplin becomes a hit with his comedy drunk act. He begins a relationship with his first love Hetty Kelly, the night before he is due to leave for America he proposes to her but she declines reasoning she is too young. Chaplin promises to return to England for her when he is a success. Chaplin is sent to America by Karno and is given a job by Mack Sennett, the most famous comedy producer in Hollywood. While there, he creates his iconic Tramp persona and due to the terrible directorial capabilities of Sennett's wife Mabel, Chaplin is allowed to direct his own movies. Before the year is over, Chaplin directs over 20 movies and after Sydney joins him in America to become his manager, decides to break away from Sennett to have complete creative control over his films and with the goal of one day owning his own studio. In 1917, Chaplin completes work on The Immigrant which causes some concern over the film's political subject matter and starts a brief romance with actress Edna Purviance. Years later at an industry party thrown by Douglas Fairbanks, Chaplin meets and begins dating child actress Mildred Harris. Chaplin eventually becomes wealthy and profitable enough to set up his own studio and becomes "the most famous man in the world" all before his thirtieth birthday. Chaplin...
The answer is:
How old was Charles in his first performance?