A small town in the United States, Jefferson Smith (James Stewart James Stewart), the leader of the local Boy Scouts and loved by teenagers, was elected as the new senator and came to Washington. He meets his father's old friend, Joseph Paine (Claude Raines Claude Rains), who is also a senator, and is infatuated with Joseph's beautiful daughter. Simple Jefferson never came to Washington, made a lot of jokes in Washington, and was teased by the media one after another. Joseph asks Jefferson to draft a proposal and asks his female secretary Clarissa Saunders (Keane Arthur Jean Arthur) to assist Jefferson. However, Jefferson discovered that his so-called senator was just a puppet in the hands of other wily senators, and he discovered a huge conspiracy. Jefferson decided to use his own weak strength against that group of people to change the corrupt political environment. Can he succeed or not? History.