The TARDIS lands in an eerily quiet and deserted London. Investigating, the boys find a calender showing 2164 AD, find a man with a headset on and see a flying saucer. The Doctor and Ian get seperated from Susan and Barbara. The girls are taken into safety by humans whereas the Doctor and Ian, at the end of the episode, are taken captive by Robomen and a familiar figure that rises out of the Thames - a Dalek!
This is an example of the advantage of episode names, not story names, as the Dalek emerging from the Thames must have given a huge thrill in 1964. Children were still wild about the Daleks. Of course, quite what a Dalek was doing in the Thames is a mystery; it could hardly have been going for a swim.
The Daleks have invaded Earth, firstly by bombarding Earth with plague weapons; secondly, they landed after major resistance was broken. As part of their invasion plan, they have captured humans, fitted them with headsets and exert control over them. The Daleks have a huge mining complex in Bedfordshire, for some reason.
Some humans have escaped and formed a resistance movement. The Doctor and Ian are taken to the Dalek ship where the Daleks want to turn them into Robomen. They are saved from this fate when the resistance attack the saucer; the Doctor gets out but Ian is forced to hide on the saucer. Everyone is split up after the failed attack (although Susan and the Doctor get reunited quickly) and head off to Bedfordshire.
The Daleks, it turns out, are planning to remove the Earth's core and replace it with a drive so they can steer the Earth around like a spaceship. The bomb they intend to use for that purpose is diverted by Ian, and it destroys the Daleks instead. The Robomen are freed from the Dalek control when a transmitter is destroyed.
This isn't quite as good a story as the Daleks but it is enjoyable nonetheless; it is inevitable that the first two stories get compared.
The Dalek voices are not as metallic or good as those in the Daleks, and the fight scenes with Daleks - like so often in the show - are poorly done as the Daleks move clumsily about. The Daleks are great to look at but silly when they get into action scenes! The Robomen talk in a monotone voice and walk stiffly. This is one of those silly sci-fi ideas - conditioned humans ought really to act and talk like we do, and that would make them frightening.
There are some lovely shots in episode 3: a Dalek stops to look around and we see the Palace of Westminster in the background; a group of Daleks are seen in Trafalgar Square and still more are seen in front of the Prince Albert Memorial. They got up very early on a Sunday morning to shoot the London scenes, apparantly.
This was, as mentioned, one of the episodes made into a film. The pic above is of one of the posters; it looks pretty cool, in a 1960s B-film sort of way.
This is also a sad story in a way. Susan falls in love with one of the resistance fighters, prompting the Doctor to leave her on Earth - the end of the original TARDIS crew. The Doctor saying goodbye is a Who moment (the scene was used to start the 1983 anniversary episode the Five Doctors):
One day, I shall come back. Yes, I shall come back. Until then, there must be no regrets, no tears, no anxieties. Just go forward in all your beliefs, and prove to me that I am not mistaken in mine.