The TARDIS materialises beside the Statue of Liberty and the Doctor and Martha step outside. Admiring the city across the water they observe the nearly competed Empire State Building, as well as a discarded newspaper that bears the headline “Hoover Mystery Deepens”.
As they make their way through Central Park the Doctor explains that following the Wall Street Crash in 1929 the huddled masses doubled in size and took up residence in the open area within the city. Sure enough the Hooverville settlement is close by, and as they wander through the makeshift town they observe two men fighting over a loaf of bread.
The town’s sheriff Solomon breaks them up and shares the loaf between them. The Doctor and Martha approach him and introduce themselves. Solomon asks the Doctor as a man of learning why America can afford to construct the tallest building in the world but still have hundred of citizens living in poverty.
Inside the building the foreman of construction is complaining to his boss Mr Diagoras about the accelerated rate of work. The smartly dressed man insists that their new masters are demanding the rate of work must remain, with the extra work on the building’s mast needing to be completed that night.
The foreman threatens to halt work and Mr Diagoras calls upon one of the masters to meet his guest. As the lift slowly rises up to meet them the foreman looks on as the door opens to reveal a Dalek, flanked on wither side by creatures resembling half-man half-pig.
The Dalek demands to know why it was summoned and Mr Diagoras explains what has been going on. He is taken away for the “final experiment” and the Dalek insists that the Empire State Building must be completed in time. They need more bodies, fast.
Back in Hooverville Solomon explains that people have been vanishing from the town and it is believed they are being abducted and the police are no interested. Soon Mr Diagoras arrives offering work in the sewers. The Doctor becomes interested in the talk of accidents happening below the ground of the city and offers to help out, taking Martha, Solomon and a young boy called Frank with them.
Soon they are below grounds being given directions to clear away a fallen tunnel. Martha talks with Frank as they make their way through the dark passageways, the Doctor enquiring into the role of Mr Diagoras, whom Solomon explains appeared almost overnight but now appears to run most of Manhattan.
Suddenly they come across a growing green brain-like entity, which the Doctor carefully examines. He then takes note that they appear to have not yet found any sign of a collapsed tunnel and ponders why they have been sent below ground.
Up above them in the Empire State Building Mr Diagoras is giving his men instructions for the constructions of the building’s mast, telling them to attach a series of panels to the base of it by the end of the night. He shows them the panels, which appear to be taken from the base of a Dalek casing.
They protest about the task in hand but Mr Diagoras warns them that they will be replaced if they do not comply. They take the panels and move off to complete their task.
Once they are gone the Dalek arrives again in the lift, explaining that the conductor must be completed for their plan to work. They move to observe the shining city below, the alien creature exclaiming that his planet is gone, yet the human race always continues. Diagoras tells it he will do anything to survive in a world, even through war.
He is unaware that in the lower levels of the building Dalek Sec is watching him. Flanked by the other members of the Cult of Skaro he claims that Diagoras is the prime example they need. He sends orders for him to be brought below ground, and his colleague above follows the orders, Diagoras following him into the lift shaft.
“Prepare the laboratory, the final experiment will begin”
Arriving at the base of the building Diagoras looks around at the strange machinery lining the walls, tended to by the strange pig servants. Before him awaits Dalek Sec, who introduces himself and Mr Diagoras identifies as the one who transmitted it’s thoughts into his mind, tempting him with such images of power. Sec orders his slaves to hold the man but he insists he wants to work with them.
Down in the sewers there is still no sign of a sewer; only inhuman squeals echoing around the Doctor and his group. They progress and Martha spots one of the pig creatures, slumped on the floor defenceless. The Doctor promises to help but is forced to retreat when more of the creatures begin to advance on him from the shadows, forcing him and the others the break into a run.
They flee through the sewers, the pig men following, and eventually they find a ladder leading up above ground. Frank however is too slow and the creatures take him with them. Solomon refuses to loose anyone else and closes the ladder’s hatch.
Suddenly Tallulah appears from around a corner; they have arrived in the theatre. Aiming a gun at them she demands to know what they have done with Laszlo. She takes them back to her dressing room and explains that her boyfriend vanished two weeks ago. She throws away the gun and explains it was a prop, before the Doctor explains that more people have been disappearing across the city, and to find out more he needs to examine the alien object he found in the sewers, which he has been keeping in his pocket.
Searching the prop stores he begins to put together a crude DNA scanner, whilst Solomon comments on his extraordinary persona. He tells him that he must return to Hooverville and wishes the Time Lord luck, whilst Martha sits with Tallulah as she prepares for the nights show.
The showgirl talks about the dismal times she lives in, always going on with the show in the hope her boyfriend will return. She explains that a white flower has been appearing on her dressing table, just as Laszlo used to do before he goes missing, and wonders why, if he is still around, he insists on being so secretive.
Back in Hooverville Solomon tells the citizens of the town that the rumours are true; people are being taken and it must be stopped. He orders them to set up sentries on duty and to arm themselves for protections.
Meanwhile, on top of the Empire State Building the construction workers fix the Dalek panels to the base of the mast, whilst below ground the Daleks prepare for the final experiment. Diagoras fears they will turn him into one of the pig slaves but Sec insists they need his flesh.
They begin to argue amongst themselves; Sec claiming that the Cult of Skaro was invented to find new ways of survival, and despite Dalek Thay’s claims that they must remain pure, Sec explains that purity has almost brought them to extinction; they must adapt to survive. Already some of the Daleks have sacrificed their components to aid the experiments and now he will sacrifice himself for the good of Dalek-kind.
He faces Diagoras and opens his casing, revealing the mutated creature within. The pig slaves drag the prisoner forward and the mutant engulfs him in it’s grasp, puling him into the bottom of the casing before slowly closing him inside.
At the theatre the Doctor focuses a stage light on the alien creature, whilst Tallulah takes to the stage to perform her number. Taking Martha with her they leave the Doctor in his examination; deducing that the creature has been manufactured.
As Tallulah begins her number; “My Angel Put The Devil In Me”, Martha watches from the wings, but spots one of the pig creatures on the opposite side of the stage. Creeping over to try and help she warns Tallulah and they race from the stage, as the Doctor determines that the creature originated on the planet Skaro…
Martha tracks the pig creature to the prop store but from there she is ambushed and dragged back down into the sewers. The Doctor follows but Tallulah is hot on his heels, theorising that whatever took her may have taken Laszlo.
The pig creatures take Martha to the rest of their prisoners, Frank standing among them, and they are marched away. The Doctor and Tallulah continue their search but are stopped when the Doctor spots the silhouette of a Dalek gliding towards them. They hide and watch as one glides past and the Doctor speaks:
“They survive. They always survive while I loose everything”
He explains to Tallulah that the Daleks are living creatures encased in metal casings, bent on destroying every creature unlike them.
In the basement Dalek Sec begins to shake and smoke from the casing, but refuses to let the experiment end; telling his colleagues to administer an injection.
In the sewers the Doctor decides to return Tallulah above ground, but run into one of the pig creatures that turns away at the sight of them. The Doctor demands to know what has been done to Martha and. the creature, still with a human voice, tells them she has been taken.
He claims that the masters turned him into a human as they have with so many others to use as slaves. Tallulah asks why he was in the theatre and the creature claims he didn’t want her to see him in is mutated form. Confessing to following her he eventually reveals himself in a shaft of light; his is Laszlo. Tallulah begins to break down in tears before agreeing to show the Doctor to the other prisoners.
Soon a Dalek arrives to inspect the prisoners and Martha warns the others not to resist. Upon hearing the name Dalek the young earthling ponders, remembering something the Doctor said to her before. Another Dalek arrives and claims the Dalekanium is in place; the energy converted is ready.
They then begin scanning each prisoner for intelligence; and as Laszlo points out from the shadows the most intelligent are taken away to the laboratory for the final experiment, the others become pig slaves.
The Daleks identify Martha as worthy of being taken to the transgenic laboratory and the Doctor hurries to join her. Laszlo tells Tallulah to return to the theatre and then walks with the Doctor. Tallulah moves off but begins to loose her way, reducing herself to tears.
Martha is relieved as the Doctor joins the group being taken above ground and soon they arrive in the laboratory, where they look on as Dalek Sec enters the final stage of evolution. The Doctor tells Martha to ask what is happening so that he is not noticed, and fighting her fear she demands to be told what the final experiment is. The Daleks tell her she will witness a new dawn of evolution; to survive the Daleks must adapt and soon the children of Skaro will walks again, free from their casings.
They turn back to Sec, whose casing opens and from within steps the result of the experiment. The human body of Diagoras has been mutated beyond recognition. His hands are disfigured so that his fingers taper to a point. His face is hidden but his brain, fused with Dalek flesh, is left exposed. A single eye looks out at the room and six tentacles lining what is left of his face stretch out at his new surroundings. The creature’s mouth opens to breathe the air around it and then it announces:
“I am a human Dalek and I am your future.”