The beautiful and evangelical figure Maria (Brigitte Helm) takes up the cause of the workers. She advises the desperate workers not to start a revolution, and instead wait for the arrival of “The Mediator”, who, she says, will unite the two halves of society. The son of Fredersen, Freder (Gustav Fröhlich), becomes infatuated with Maria, and descends into the working underworld. In the underworld, he experiences first-hand the toiling lifestyle of the workers, and observes the casual attitude of their employers (he is disgusted after seeing an explosion at the “M-Machine”, when the employers bring in new workers to keep the machine running before taking care of the men wounded or killed in the accident). Shocked at the working conditions, he joins her cause. Meanwhile his father Fredersen learns of the existence of The robotic Gynoid built by the scientist Rotwang (Rudolf Klein-Rogge) (Rotwang wanted to give the Robot the appearance of Fredersen’s dead wife Hel) and orders Rotwang to give the Robot Maria’s appearance. By doing so he wants to spread disorder among the workers what would give him the pretext to carry out a retaliatory strike against the workers.
The real Maria is imprisoned in Rotwang’s house in Metropolis, whilst the robot Maria becomes an exotic dancer in the city’s nightclubs, fomenting discord amongst the rich young men of Metropolis. The workers are encouraged by the robot Maria into a full-scale rebellion, and destroy the “Heart Machine”, the power station of the city. However, the destruction of the machine leads to the city’s reservoirs overfilling, which floods the workers’ underground city and seemingly drowns their children, who were left behind in the riot. When the workers realise this, they attack out into the gridlocked and confused upper city, foreshadowing the “destruction of the enemy in the citadel” ending still seen in films. The crowd breaks into the city’s entertainment district and capture the robot Maria, who they believe is responsible for drowning their children. They burn the robot at the stake, and when Freder sees this, he believes that it is the real Maria and despairs. However, Freder and the workers then realise that “Maria” is in fact a robot, and see the real Maria being chased by Rotwang along the battlements of the city’s cathedral. Freder chases after Rotwang, resulting in a climatic scene in which Joh Fredersen watches in terror as his son struggles with Rotwang on the cathedral’s roof. Rotwang falls to his death, and Maria and Freder return to the street, where Freder unites Joh and Grot, the workers’ leader, fulfilling his role as the “Mediator”.-WikiPedia
As a side note, Lillian Gish was originally cast as the character of Maria but the German producers wanted one of their own actresses for the part, hence the casting of Helm.
