This episode literally starts out with a bang, as gases erupt from an opening in the sea bed. It quickly proceeds to a rather ghastly scene, as a hapless diver is devoured (all right, we don't actually see it, but it comes close) by a gigantic sawfish.
Following the opening credits, we are treated to a pleasant view of Nelson's office at the Institute. Cara Sloan is there, trying to persuade Nelson to accompany her back to the undersea habitat. This is where we find out that the Nelson Institute is swamped with requests from scientists (all over the world, presumably) for the use of Seaview's facilities.
This is where the questions begin. Why doesn't Cara simply tell Nelson what is going on? We don't hear just what her original arguments were, but Nelson obviously didn't think that they were worth following up. When Sterling calls from the habitat and drops the little tidbit about a natural fissure extending down to the earth's core, Nelson chokes on his cigarette and promptly agrees to come. And why not tell him about the frightening side effects, and the resulting tragedy? That would have made it more imperative for Seaview to check out the situation.
Captain Crane's romantic endeavors were limited to that cute beach scene in "...and Five of Us are Left." However, this episode makes it clear that he still has an eye for the ladies. Stu Riley and Chip Morton both comment on it in two different scenes. Riley's scene includes a statement from Chief Sharkey as to why women should not be allowed on ships. It's a rather bizarre monologue, as he uses the same "surferspeech" as Riley does. Riley must be having an influence on him.
After assuring that she will be given a salt-free diet (to Sharkey's annoyance) Cara slips into the galley and contaminates the salt supply. This might not have worked nowadays, with everyone concerned about their sodium levels, but back then it was a very clever idea. On the other hand, all Cara contaminated was the big cannister of salt. I don't know how things go on a working submarine, but it doesn't seem logical that all the salt shakers would be emptied out and refilled on a daily basis. The bigger question, of course, is why she did it in the first place. We can be charitable and assume that Cara and Sterling were already being affected by the strange gases (it's possible that not all of them dealt with growth) because the whole idea of using hallucinogens on the crew was, quite frankly, stupid. There was a very good chance that the Seaview would be badly damaged as the crew reacted to things they were not actually seeing. There was another good chance that, having determined that they WERE seeing hallucinations, the crew would NOT react on being confronted with the real thing, and the Seaview again would risk being damaged. Which, of course, is exactly what happened.
More questions rise. Why were all the hallucinations seen outside the sub? You'd think they would be seeing things on the inside, as well. Everyone presumably had different levels of the hallucinogen in them, depending on their taste for salt, but everyone reacted as though they were all seeing the same things, at the same times. Nelson's explanation for why the Seaview's equipment (not affected by hallucinogens) responded to the hallucinations was a little glib. And why did Cara wait so long to put forth her "theory" that the open fissure was emitting hallucinogenic gases or radiation? Interestingly, it was Crane, not Nelson, who realized that, as a self-contained environment, the Seaview should not be affected by outside gases (and their equipment should pick up radiation levels). He seemed certain that the source had come from inside the Seaview--he just didn't take it far enough. (Swayed by a pretty face, I suppose.)
Cara was remarkably casual about taking flight in a high-powered craft piloted by a man under the influence. They made it to the habitat, where they found Dr. Sterling definitely under the influence. Oddly, it didn't occur to Nelson that he might still be seeing things. Presumably the gases were partly responsible, but Sterling turns out to be yet another paranoid scientist, convinced that Nelson can't "understand" the value of his work. It also doesn't occur to him that, even if they close up the fissure, they can always open it up again for more investigations at a later date.
Having knocked Nelson out and grown still more, Sterling manages to squeeze out of the habitat. Inexplicably, his teeth have grown out of proportion to the rest of him, giving him a gruesome appearance. Confronted by this apparition (and again, not considering that they might still be seeing things) Crane promptly orders missiles fired--which somehow miss, even though Sterling at the time was standing directly in front of the sub. Sterling gives a good underwater impression of a small boy having a tantrum and trying to smash one of his toys. Crane finally sends a charge through the hull (which seems to be S.O.P. when dealing with oversized creatures) finishing off Sterling--and also Cara, who loved not wisely but too well.
Questions aside, it was a fun episode, and beautifully shot.
It would be interesting to know just what, if anything, was done about all those oversized sea creatures in the vicinity.