请说明电影《肖申克的救赎》的主要情节。
The main plot of the movie "The Shawshank Redemption" follows the story of Andy Dufresne, a successful banker who is wrongly convicted of murder and sentenced to life in Shawshank State Penitentiary. 

In prison, Andy befriends another inmate, Red, and makes a name for himself by using his banking skills to help the prison guards with their investments. 

Despite facing numerous setbacks and challenges, including physical abuse and corruption within the prison system, Andy never loses hope and continues to plan his escape. 

Eventually, with the help of Red and other fellow inmates, Andy successfully tunnels his way out of the prison and escapes to freedom.