"Invaders from the Fifth Dimension" is not only one of the best episodes of the series, it is an excellent science fiction film/story in itself.
I won't go into the plot, as you can just read the synopsis. This review will focus more on the technical aspects of the episode.
I'll first touch on the acting. Every cast member gives 100 percent, but the stand-out will go to Bill Mummy and Jonothan Harris. Most scenes involve just the two of them. Their characters are very prominent, Will being very intelligent, yet thoughtful and caring about everyone's feelings, even Dr. Smith. Dr. Smith is ruthless. He really does admire Will, and probably cares about him (though to a very limited extent). Yet Smith will do absolutely anything to save himself, offering "the Robinson tribe" to the aliens first, then ultimately Will.
One outstanding scene involving Will and Smith is when Will is starting to doubt that Dr. Smith is being truthful. As Will tries to drink some water, Smith warns him that it is actually acid. When Will shows disbelief, Smith steps back and tells Will to go ahead and touch it. Will tries to put his hand to the water, but keeps looking back at Smith, who is really putting Will to the test. Afraid to touch the water, Will apologizes to Smith, and they move on.
When watching, one can tell that much time and thought went into every aspect of this episode. The black and white film used adds to the sinister atmosphere, and the cinematography is excellent. There are several scenes where the camera pans slowly to the left or right to reveal something, and the timing is perfect. The score is also excellent.
There are some great dialog moments in this episode, but my favorite is when Smith and Don are standing near the alien spaceship. Don, seeing the ship for the first time, says "so that's the monster." Smith says, "Now, that doesn't look very monstrous, does it?" Don reply's to Smith, "Niether do you".
If I had more time, I could go on. I'll just say, LIS fan or not, this episode is worth watching, along with several episodes from season one. A quality piece of work.
James.