Things start out innocently enough, on pretty little Murrow Atoll, 800 miles west of Chili. Bainbridge Wells (who, unlike every other scientist we've seen on this show, does not have a scholarly title) has brought his camera team to shoot another thrilling installment of his television series, "Science on the Move." There have been stories about a "sea monster" in the vicinity of the atoll, and Wells has come to investigate. He's brought an electronic ultrasound device to lure the creature out (and presumably drive the other local fauna nuts as well). Naturally, just as he vocally queries the existance of a monster, we see the water in the lagoon begin to boil. Wells trails off as he stares at the vaguely humanoid, spiky greenish thing that rears out of the water, looking and sounding somewhat peeved. Rather than hurling his ultrasonic gizmo as far out into the lagoon as possible, Wells simply tosses it in front of his cameraman and flees. The cameraman courageously (if not sensibly) keeps his camera focused on the monster until it strides up and grabs him. The remaining crew are summarily dealt with, then the monster heads for home.
We next see the Seaview getting loaded and prepped for her next mission, which may be changing unexpectedly--Bainbridge Wells is on board, having an interview with Nelson. As Crane and Morton discuss this (and speculate on Wells' chances of convincing Nelson) Patterson looks up from where he has been working, and then oh-so-casually drifts closer to the officers.
Nelson dislikes what Wells stands for--a glory hound with few actual academic credits who uses science for his own selfish ends. (This harks back to Nelson's irritation at the publicity-mad Bentley Falk of the first season's "The Condemned".) Wells puts a spin on the situation--simply by changing the phrase "sea monster" to "New Biological Species". Nelson admits that he's intrigued, but without more proof, there's no point in going further. Wells provides proof--a single snapshot of the creature (taken while he was hiding, no doubt) as well as the negative. Nelson decides that it's worth looking into.
Way back in the pilot episode, Nelson had mentioned that the crewmen of Seaview had secondary fields of expertise. Over two seasons later, we find that Patterson's specialty is photography. His first duty watch, as they get underway, is in Seaview's Photo Lab. This is an odd point, as Sharkey points out that Patterson is supposed to be on emergency leave. (Patterson blithely replies that he cancelled it.) To receive emergency leave, they would, of course, insist on knowing what the emergency was. It's a virtual certainty that the emergency was dealing with the death of his father. What reason could he have had, at that point, to conceal anything?
Patterson is called to Nelson's cabin to take Wells' photograph and blow it up. It's at this point that we learn that Wells had claimed that his television crew had died because his cameraman panicked.
A comic relief scene is tossed in here. In the Missile Room, Kowalski is putting 40,000 units of Anodyne into a small missile--just in case they have to tranquilize the monster. Someone royally messed up here; that missile was relatively small, but if it had been used, it would have cut the monster in half, at the very least. Patterson, who has stopped by to requisition some developing fluid for the Photo Lab, is waylaid by Sharkey, who wants him (when he has time) to blow up a rather blurred photograph of a young woman. Sharkey is quite proud of his trophy--until Patterson mentions that Kowalski has an identical photograph. Sharkey promptly threatens the blameless Kowalski with being put on report, to 'Ski's bewilderment.
Having arrived at the atoll, Patterson approaches Crane and requests that he be allowed to dive in the lagoon. Chip Morton is very put out; such a request should properly go through channels (namely, him). Patterson suggests that they will want to send a team out, and he would like to be on it--but he still wants to go out even if they don't send a team. Oddly, Crane doesn't ask why at this point. Nelson almost immediately walks up and announces that he wants a cameraman to go out in the lagoon. Patterson promptly announces that he is the best cameraman on board. No false modesty here, and in fact, he may be speaking the simple truth--he will later tell Wells that he's an expert. Crane finally asks why Patterson is so insistant on going out. Patterson has a very good reason for wanting to search the lagoon for any evidence about the deaths of the television crew--his father was the cameraman, and he is quite certain that his father would not have panicked. Aside from looking at each other, Crane and Nelson don't react much. A "Sorry to hear that, Patterson" would have been nice.
Patterson prepares for his dive, and Sharkey insists that he not go alone--according to the "book", no diver is to go out alone. I've pointed this out several times--Sharkey seems to have forgotten that Crane and Nelson tend to ignore this point. Chip Morton agrees with Sharkey, but, because of the uncertainly of the situation, tells Sharkey to ask for a volunteer. Sharkey--perhaps still smarting over the photograph incident--"volunteers" Kowalski.
The whole next sequence is one of those aggravating points. I suspect that it may have been due to clumsy editing. Patterson and 'Ski start seaching the lagoon. They locate the camera tripod, which means that the film magazine may not be far away. Meanwhile, on Seaview, sonar (or radar) has picked up something huge in the vicinity, and Crane recalls the divers. A few moments later, Patterson finds the magazine and shows it to 'Ski. Crane calls them again, wondering what's keeping them. 'Ski reports that Patterson is refusing to leave. The problem is, at this point Patterson has no reason to remain in the lagoon, and every reason to want to get back inside as quickly as possible. The large shape has disappeared from the instruments. Chip goes to the nose to see if it can be spotted visually, while they check the charts to see if there are any natural formations that might be hiding the creature, which seems to be a giant economy sized version of the human-sized monster. Nelson then spots a blip on the sonar separate from the two blips of the divers--this one is the human-sized monster, heading right for the divers. Patterson at this point, still seems to be frozen in admiration for his cleverness in finding the magazine. The small monster attacks the divers. This whole sequence would have made perfect sense if they had shown Patterson finding the magazine just prior to the monster's attack.
At the same time that the divers are attacked, the big creature (who apparently had managed to hide somewhere) suddenly looms up right in front of the Seaview. (Here's where that tranquilizer missile might have come in handy, but they decide that 40,000 units of Anodyne won't be enough.) The small creature knocks out the two divers, then swims away. Big Guy, on the other hand, grabs the Seaview and rams it into the seabed, with predictable results inside. Surprisingly, there's minimal damage. Crane orders everyone to keep as quiet as possible--they're going to play dead and hope that the monster leaves. Wells becomes panicky, and Nelson, looking exasperated, hauls him out of the Control Room. Big Guy finally moves away. They've got to get to the surface--but there's the matter of the two divers, whose radio links have been disconnected during the fight. Chip Morton prepares to give orders to blow ballast; they can't afford to wait. Outside, Patterson has revived, and he shakes Kowalski awake. Clutching the magazine, they head back for the Seaview.
Having delayed as long as possible, Crane finally gives orders to lift off from the bottom. Sharkey offers to lead a search party, but there's no time. Sharkey turns and snaps angrily at the crew to clean up the area--and then hears a knocking on the hull. He leaps (literally) for the microphone. Hearing the news, Crane rushes down to the Missile Room. Crane's reaction would probably be instantly recognized by any parent--worried sick about his men, then finding them safe, he responds with a bellow of rage. Patterson quietly accepts responsibility for himself and Kowalski, and shows Crane the precious magazine, which he had brought in at the expense of the (presumably very expensive) underwater camera. (Why he couldn't have 'Ski carry the camera, I don't know.) Crane cools, but not very much; he orders Patterson to confine himself to quarters, promising to deal with him later.
Wells shows up at Nelson's cabin, upset that they are heading for home rather than going after the monster again. Nelson dryly reminds him of his previous panic. Wells admits that his career is on the line; there has been some question as to the deaths of his men. Positive proof of the existance of a new species would help him immeasurably (and oh, yes--it would be useful to science). Wells suggests that they try getting at the creature from the shore, rather than fighting it in its element. Crane shows up at this point, carrying the magazine.
It's always annoying when, for purposes of plot, lead characters are forced to act like total idiots. Nelson and Crane are both aware of Patterson's desire to exonerate his father. If his father was innocent, that means that Wells had lied about the incident. Patterson risked his life, Kowalski's life, and the whole Seaview to find that film magazine, certain that it was a valuable piece of evidence...and Nelson casually hands it over to Wells, while Crane stands there and doesn't react in the slightest. Nelson announces that he has decided to go back and try to capture the creature. Crane protests, but, as usual, he gives in.
Patterson sins twice over--not only slipping out of his quarters against orders, but coming up to Officers' Country in search of Captain Crane. Sharkey, spotting him, tries to get him out of the way, but Crane comes up at that moment, and allows Patterson to speak. Patterson wants to take the film magazine--he's certain that he can salvage some of it. David Hedison put in a nice, brief reaction here; he glances towards Sharkey with an "Uh, oh" look on his face, before telling Patterson that the magazine had been given to Wells. Patterson is, quite understandably, shocked, but his reaction is quite restrained--had it been me, I think I would have been tempted to slam Crane into the wall, while using some of the vocabulary popularly ascribed to sailors. Sharkey hustles him off. Crane at least has the decency to look after them with a troubled look on his face, perhaps acknowledging (if only to himself) that he blundered, as well as causing a serious breach of faith with his crewman.
A surprisingly small team--Nelson, Wells, Sharkey and Kowalski--row up on shore, armed with the ultrasonic device and double-charged tranquilizer guns. They pause to secure the rubber boat--and naturally, that's when the creature shows up, attacking from inland rather than the water. Nelson trips in the sand and is cornered, but Sharkey hits it with two shots and the monster keels over.
Patterson, meanwhile, has sneaked into Wells' quarters and stolen (or rather, repossessed) the film magazine.
The creature is ensconced in the holding tank in Nelson's lab. They seem to be treating it as an air-breathing mammal, rather than a creature that can temporarily exist in the open air--the tank is dry. Wells is thinking of all the publicity he will be getting. Nelson, of course, is disgusted with him. They discover that the big creature is back on the scene and heading straight for them. Nelson elects to run rather than stay and fight, and they go to flank speed.
Patterson goes to the lab to make use of the film projector there (you'd think that there would be one in the Photo Lab). Wells shows up. The confrontation is superb; Patterson is perfectly cool, but with an underlying edge. They watch the rather spotty film, which clearly shows Wells turning the creature on his men in order to escape himself. Incredibly, Wells thinks that Patterson will overlook his father's death and ruined reputation for money (people tend to judge others by their own standards). Patterson, of course, responds as you would expect. The ensuing fight knocks over the ultrasonic device, turning it on. Patterson defends himself pretty well, but is finally knocked out. At this point, the creature awakens and goes after Wells. I suppose his death was inevitable, but I would much have preferred that he live and face the consequences of his actions.
An alert sounds from the lab (presumably set off when the creature broke through the holding tank, because certainly neither Wells nor Patterson turned it on). Nelson finds his lab in a shambles and Wells dead. Patterson is injured (though not as badly as it seems at first). Patterson's only thought at this point is the film, and the fact that he had proven his father's innocence. (One hopes that the film was not wrecked by the creature.) Sharkey and 'Ski go after the creature with their trusty trank guns, but this time, not even multiple shots stop it--it seems to have quickly developed an immunity. Nelson nearly gets cornered again, but manages to get away--extremely annoyed with his men, until he learns about the tranquilizer. Nelson decides that it's time for some personal heroics and orders Crane to keep everyone away from the Missile Room--after the mini-sub has been raised clear of the floor hatch. He gets back to the lab and fetches the ultrasonic device, switching it back on, then crawls into the air vents. Sharkey wants to do SOMETHING to assist the Admiral, but Crane insists that they follow his orders--at least until he learns that the creature is heading right for the Missile Room. At this point, he decides that the orders don't apply to him, and rushes down to help. He could have saved the effort--Nelson easily decoys the creature into dropping into the bottom hatchway to freedom--which no doubt mollified it considerably. Patterson is reported to be in pretty good shape--but is he supposed to be under arrest? Having been more or less responsible for Patterson's violation of orders, Crane orders him released.
They are left thinking that someday--better prepared--they will come back and try to find the creature again. Nelson is annoyed that Wells will be getting the credit that he wanted. This, again, harks back to the first season's "The Condemned"--where another man was up for posthumous honors he did not really deserve. I would like to think that Patterson's evidence would balance the scales somewhat.