Only Dr. Who and Susan were retained from the first film. The parts of Ian and Barbara were replaced by constable Tom Campbell and Dr. Who's neice Louise. The constable witnesses the robbery of a jewelry store and goes to the nearest Police Box which is really the T.A.R.D.I.S. and opens it just as Dr. Who cuts out the magnetic locks. The constable collapses shortly after entering the ship. Dr. Who looks at the scanner and sees that things are getting a little wild outside, so he takes off only to materialize in 2150 AD where London is a burnt out husk. What follows is a fairly straightforward adaption of the serial to the big screen other than a few cast/character changes even down to the iconic scenes of a Dalek coming out of the Thames and a Dalek saucer flying over London.
As in the original serial, the movie featured a lot of location filming. To me, this movie was less dated than the first one and was quite enjoyable. It also featured two actors who would later appear in the series proper: Philip Madoc (who played several roles on the series including the War Lord in The War Games and Doctor Solon in The Brain of Morbius) and Bernard Cribbins (Donna Noble's grandfather in the revived series). The only thing that dates it a bit is the fight music (i.e. when they storm the Dalek ship)... it reminds me a bit of the music in the 60's Batman series. :)
In the original serial, the Doctor left Susan behind after she fell in love with one of the rebels. That obviously wouldn't work in this film since Susan is a little girl in these movies. That necessitated a few plot changes. The most notable change was putting different sets of characters in the same situations (i.e. Barbara and a female rebel in the serial were replaced by a male rebel and Susan in certain sequences). The "intelligence test" in the cells was a bit different and the ultimate defeat of the Daleks was completely different from the serial... in fact, I thought it was a bit silly looking in the movie: the bomb falls down a shaft, is diverted by a couple of board and slides down another shaft at an angle. The original serial had Ian block the shaft entirely with boards.
Most of the major differences were just scale-wise. The model shot of the Dalek ship flying over London was more impressive than the shaky model shot in the serial (which can be replaced by CGI using an option on the DVD). The wires were visible in a couple of cases in the movie, but impressive, none-the-less. ;) The set of the exterior of the Dalek ship was more impressive, the chase sequence with a rebel escaping from the ship to be killed by the Daleks was more action-packed, etc. The Daleks were once again fitted with smoke projectors instead of ray guns... proving once and for all that second-hand smoke can kill... or would that be second-plunger smoke... ;)
As I said, a very enjoyable and impressive adaptation, but for some reason or other, it didn't do as well at the box office as the first film, so it was destined to be the last Dalek feature film. :( I purchased a DVD box set that included excellent transfers of both films and, on a bonus disc, a direct to video documentary of the making of the films called Dalekmania which was made in 1995, the 30th anniversary of the first film. In it, they interview several of the cast members and crew about making the films. They also included a few interview clips with Terry Nation. Surprisingly Bernard Cribbins wasn't on there. The interview segments are interspersed with scenes of a mother taking her two children to the theather and them getting transported to the world of the films. All of the theater staff in these segments is played by none other than Micheal Wisher (Davros) in one of his final roles. :) While the theater segments were a bit silly, overall the documentary was very good and consistent with the type of behind the scenes material you'd find on a movie DVD.
Now that we've explored the alternate universe, it's time to move back to the real universe and start the Patrick Troughton stories... with more Daleks... in The Power of the Daleks... sadly lost. :(
It's going to be several days before my next post as I watch the serial and deal with the loss of my mother. :( Stay tuned, though. I'll be back in a few days. :)