The Doctor (William Hartnell), his grand-daughter Susan (Carole Ann Ford), and her teachers Ian (William Russell) and Barbara (Jacqueline Hill) have travelled through space and time and landed on "The Dead Planet"--the original title of this story. In a strange, otherworldly petrified forest they spot a huge city in the distance, which also appears to be dead.
Susan is certain that someone or something touched her shoulder in the dark, but the others don't believe her story until they hear a knock on the TARDIS door and find an object on the ground outside. The Doctor insists on investigating the city and they make their way there. Doors open at a touch, but the hallways and corridors of the city still seem deserted. They separate (obviously never having seen a horror movie) and Barbara, lost and terrified, stumbles upon the Daleks.
The Doctor's greatest foe over the years was thus introduced in the second Doctor Who story. Trapped in their rolling metal coffins, all of them quite insane, the Daleks appeared again and again on the series and quickly became fan favourites. Personally, I find their tinny staccato voices highly irritating, but it does add to their air of homicidal hysterics.
Their origin on the planet Skaro is revealed to the time-travellers. Five hundred years before, the Daleks and the Thals barely survived a nuclear war. The Thals, according to the Daleks, live horribly mutated in the dead forest, but the Daleks built machines to house and protect their bodies and lived underground in the city. But the whole planet is contaminated with radiation and the time-travellers are becoming ill, so Susan, who is youngest and strongest and who knows how to unlock the TARDIS, is allowed to leave to fetch the medicine which the Thals have left for them. The Daleks intend to track her and wipe out the Thals for good. Susan discovers that the Thals are not horribly mutated; they are in fact handsome, noble, well-spoken pacifists. The Daleks dictate a letter by Susan promising food if they will come to the city to talk peace. It is, of course, a trap.
Meanwhile, there are various harrowing escapes and imprisonments, alarums and excursions. In the most interesting, the time-travellers discover a way to ground and short out a Dalek, rendering it inoperable. Ian and the Doctor open up the survival suit and reveal the mutated monster inside (though not to the audience or to Susan and Barbara). Ian climbs inside and his voice sounds like a Dalek, so he pretends to be taking the others for questioning.
At the climax, it appears the Daleks are dying and need more radiation, which is ironically keeping them alive, so they intend to set off another Neutron Bomb, which will exterminate the Thals. The Doctor seems willing to take off and leave them to their fate, but Ian must convince the Thals to go to war.
The Daleks were made of plastic and plywood. Small actors sat inside, usually in their underwear, and rolled the things around on casters by shuffling their feet, looking out through black gauze and operating the swivelling lids, the ray-guns, and the...well, toilet plungers. Blinking lights told the cameramen which Daleks were speaking in each scene. A device called a ring modulator changed their voices to sound mechanical, but the voice of the actor remained distinct and they soon began to shake or swivel or move to create body motion during their speeches. Rumours of the Dalek design being based on the saltshakers in the BBC commissary are apparently true.