Continuing his pursuit of the mysterious young woman, Freder enters the squalid, smoky, labyrinthine underground work area through door V, where in the Gothic depths, he is overwhelmed by the heat. He notices an exhausted worker, number 11811 (Erwin Biswanger), struggling with an electricity-routing device -- a large clock dial. The worker must match up lighted bulbs on the clock's rim with the two hands of the clock during his ten hour shift. As the sweating worker collapses in his arms, he greets him as "Brother." The worker revives and pleads: "...the machine...Someone has to stay at the machine!" and Freder sacrificially proposes to take his place at the dehumanizing, tiring machine:

Someone will stay at the machine...ME! Listen to me...I want to trade lives with you!

Freder switches clothes and identities with underground worker 11811, and gives him a note specifying the location of Josaphat's apartment, telling him to go there and wait for him. As 11811 leaves in Freder's chauffeured car (followed by the Thin Man), he betrays his promise and visits a red-light district instead. "Finding money, lots of money, in Freder's clothes, he succumbs to the temptations of the city and the night. Instead of going to Josaphat's apartment, he has himself driven to Yoshiwara, Metropolis' entertainment district."

The next title card reads: "In the middle of Metropolis, there was a strange house, overlooked by the centuries." It is the rickety old residence of Rotwang (Rudolf Klein-Rogge), an alchemist and inventor. The wild-haired, demented scientist with a black-gloved right hand is summoned to speak to Master Joh Fredersen in one of the home's high gloomy rooms, and as he waits, he draws open a curtain concealing a small alcove. There on a pedestal "as wide as a wall and as tall as a man," he sees the stone head of a woman - with the word HEL engraved on the pedestal of the statuette. Below HEL, he reads:

BORN FOR MY HAPPINESS AND MANKIND'S BLESSING, LOST TO JOH FREDERSEN. DIED GIVING BIRTH TO FREDER, JOH FREDERSEN'S SON.

Rotwang silently enters the room with the monument, and furious - he tears closed the curtain in front of the bust. "The angrier Rotwang becomes, the calmer grows Joh Fredersen." Evidently, there was something of a love triangle between Hel, also a love interest of Rotwang, who married Joh but died during Freder's birth. Joh attempts to calm the raving, embittered scientist: "Let the dead rest in peace, Rotwang...For you, as for me, she is dead..." However, Rotwang rebuffs Joh: "For me, she is not dead, Joh Fredersen, - for me, she lives -- !"

In his efforts to recreate or replace Hel with a robot, Rotwang lost his hand. He asks Joh: "Do you want to see her - ?" -- and reveals his ultimate robotic creation - a beautiful, fully-functioning android robot that is instructed to stand up, slowly walk forward, and extend its hand toward Joh. [Rotwang's goal is to turn a machine into a human, while Joh has long been treating the working class of men like machine-automatons to service larger machines.] Rotwang exclaims:

Isn't it worth the loss of a hand to have created the man of the future, the Machine - Man - ? ! Give me another 24 hours - and no one, Joh Fredersen, no one will be able to tell a Machine-Man from a mortal - - ! The woman is mine, Joh Fredersen! The son of Hel was yours!

The real reason for Joh's visit is to seek advice - to have Rotwang decipher the meaning of the secret worker diagrams-plans discovered by Grot in workers' clothes.

Meanwhile, back toiling at the tiring job of the worker, Freder (who has discovered a copy of the diagrammed map/plans in his pocket) is confided in by another worker, and told that at the end of the shift, at two o'clock, there is a secret meeting in the ancient catacombs: "She has summoned us again..." Visual images of the dials on the machine and the ticking work clock merge back and forth. He cries out from the clock, as the crucified Christ cried out from the cross: "Father -! Father -! Will ten hours never end -- ??!!" After the painstaking shift that finally ends, Freder joins other exhausted workers as they file down into the deep catacombs, where they have been summoned.

At the same time, Rotwang interprets the meaning of the secret hand-drawn map/plans: "- it is a plan of the 2000-year-old catacombs deep below the lowest levels of your Metropolis." [Catacombs were the location where ancient Christians hid from persecution.] Concerned, Joh says: "I should like to know what my workers are doing in the catacombs." Rotwang descends with Joh to his basement where he opens a trap door, with stairs leading down into the catacombs. Workers are also assembling in the subterranean, darkened catacombs to see Maria - and Freder is stunned to again see the wistful, Christ-like, angelic, light-haired young woman standing on an altar decorated with tall crosses and lighted candles behind her. A spiritual leader, she preaches to her raptured comrades, as Rotwang and Joh spy on the congregation from a secret vantage-point. She makes an obvious analogy between the tower-building in Babel (recorded in the Biblical book of Genesis), and the workers who build and maintain Metropolis - she speaks about how the conceivers of Babel mistreated the slaves (similar to how the rulers of Metropolis are uncaringly exploiting their downtrodden workers):

Today I will tell you the legend of THE TOWER OF BABEL...(Flashback) Come let us build us a tower whose top may reach unto the stars! And on top of the tower, we will write the words: Great is the world and its Creator! And great is Man! ...but the minds that had conceived the Tower of Babel could not build it. The task was too great. So they hired hands for wages. (Streams and columns of naked, bald and chained slaves surge toward the tower from five directions) But the hands that built the Tower of Babel knew nothing of the dream of the brain that had conceived it. BABEL. (Thousands of slaves labor to move large slabs of rock - the words BABEL begin dripping blood) One man's hymns of praise became other men's curses. People spoke the same language, but could not understand each other. (Maria clutching her left breast) HEAD and HANDS need a mediator! THE MEDIATOR BETWEEN HEAD AND HANDS MUST BE THE HEART!

The workers in the audience sink down to their knees, as the beautiful Maria urges them to peacefully seek compromise and await their salvation by a divine mediator, coming between the rulers and the ruled. One worker impatiently asks: "But where is our mediator, Maria - ?" A spotlight shines on Freder in the crowd, as he beats his chest in agony. She answers and she looks upward, urging them to wait for their salvation: "Wait for him! He will surely come!" Another restless worker threatens: "We will wait, Maria!...But not much longer -- !" As the assembly disperses, Freder and Maria gaze toward each other, each clasping their left breast above their heart. She approaches him and asks: "Oh mediator, have you finally come?" He affirms his commitment: "You called me -- here I am!" And they kiss for the first time. She tells him to meet her in the cathedral the following day: "Until tomorrow, in the cathedral!" and they kiss a second time as he departs.

After discovering the workers' clandestine meeting, Freder's controlling, glacial father conspires with mad scientist Rotwang to create an evil, robotic Maria look-alike duplicate, in order to manipulate his workers and preach riot and rebellion. Fredersen could then use force against his rebellious workers that would be interpreted as justified, causing their self-destruction and elimination. Ultimately, robots would be capable of replacing the human worker, but for the time being, the robot would first put a stop to their revolutionary activities led by the good Maria: "Rotwang, give the Machine-Man the likeness of that girl. I shall sow discord between them and her! I shall destroy their belief in this woman --!" After Joh Fredersen leaves to return above ground, Rotwang predicts doom for Joh's son, knowing that he will be the workers' mediator against his own father: "You fool! Now you will lose the one remaining thing you have from Hel - your son!" Rotwang comes out of hiding, and confronts Maria, who is now alone deep in the catacombs (with open graves and skeletal remains surrounding her). He pursues her - in the expressionistic scene, he chases her with the beam of light from his bright flashlight, then corners her, and captures her when she cannot escape at a dead-end.

The next day, Freder vainly searches for Maria in the cathedral. He listens as a monk in the pulpit preaches:

Verily I say unto you, the days spoken of in the Apocalypse are nigh!...(The monk quotes from the Bible) And I saw a woman sit upon a scarlet-colored beast, full of names of blasphemy, having seven heads and ten thorns. And the woman was arrayed in purple and scarlet color, having a golden cup in her hand. And upon her forehead was a name written, mystery, Babylon the Great, the mother of abominations of the earth.

Freder then addresses a life-sized statue of the Grim Reaper in a display of seven statues representing the Seven Deadly Sins: "If you had come earlier, you wouldn't have scared me. But now I beg you: Stay away from me and my beloved!" Disappointed that Maria doesn't show, he goes to Josaphat's home, hoping to find Worker 11811. But after his night in Yoshiwara, Worker 11811 has been caught by the Thin Man and sent back to his machine. Freder tells Josaphat that he will continue to look for Maria: "I must go. I must look on my own for the person to whom 11811 was supposed to lead me." Soon after Freder leaves, the Thin Man forced his way into Josaphat's apartment and tried to get him to leave Metropolis. He tried bribes and threats, but Josaphat couldn't stop thinking of the man who trusted him - Freder. However, Josaphat was overpowered by the Thin Man when a fight broke out.

In Rotwang's laboratory, the Machine-Man sits, looking like an Egyptian deity. Light streams from above. Rotwang takes its hands and speaks to it, revealing his ultimate diabolical plan to displace Fredersen as Master and to take power himself:

You will destroy Joh Fredersen - him and his city and his son.

Then Rotwang threatens the kidnapped Maria, stalking her and announcing his intentions: "Come! It is time to give the Machine-Man your face!" As he bends her over a table, she screams out - and her cries for help through a grating in the ceiling are heard by Freder, who happens to be walking by in the street. Freder attempts to save her (and enters Rotwang's residence, but is trapped inside by doors that open and close on their own), but her pleas are muffled by Rotwang, and she is taken deeper into his laboratory. He calls out for Maria, knowing she is there after finding her scarf, but he cannot locate her.

In the film's most celebrated creation-transformation scene set in Rotwang's laboratory, the mad scientist has attached Maria (lying horizontally in a cylindrical clear chamber/capsule) by wired connections and a helmet to the Machine-Man. His laboratory is filled with bubbling beakers of liquid, dials, switches, flashing electrical circuits and arcs, and other contraptions. When he turns a switch, lightning sparks of energy descend from a round ball in the ceiling to the head and foot of the cylinder. Luminous, glowing rings surround and move vertically atop the standing robot, as its circulatory system is energized with Maria's life force, and Maria's face dissolves onto the face of the android. The real Maria loses consciousness as the robot likeness becomes flesh and blood.

After his experiment is a success, Rotwang releases the trapped Freder, who immediately asks: "Where is Maria-?" He is told: "She is with your father."

In the next scene, the evil, lusty Maria android, portrayed with her left eye drooping slightly shut, is in the office of Master Fredersen - he orders her to initiate his plan:

I want you to visit those in the depths, in order to destroy the work of the woman in whose image you were created!

Freder rushes in, completely disoriented (the camera image rotates and flashes) to find Maria in the arms of his father, and he collapses, falling dangerously ill. On his sick bed, the feverish, delirious Freder notices an invitation given to his father from Rotwang - who "requests the pleasure of your company at dinner and to see a new Erotic Dancer." A group of wealthy, tuxedoed men, including Joh Fredersen and Rotwang, watch as the false Maria rises on a stage platform in the depraved nightclub, and begins her sexy, tempting performance of an almost-nude (with pasties on her breasts), hip-swiveling Salome-style dance. The lustful men in the audience watch in amazement - their lecherous, staring eyeballs seen in a montage. The erotic dancer is portrayed as the one that the cathedral monk had spoken of, the lascivious whore of Babylon riding on a beast with seven heads. "For her - all seven deadly sins!" The distraught Freder imagines, in an hallucination, that the Grim Reaper statue comes to life, playing a leg bone like a flute during her dance. In his vision, the Reaper swings his sharp scythe and cries out: "Death descends upon the city -- !"