It opens, as usual, in the Control Room, with everyone busily intent, awaiting the arrival of a cargo plane overhead. Dr. Bradley, Allied Defense Commission Bomb Expert, is conferring with Nelson and Crane when Sharkey arrives to speak with the Admiral. Bradley addresses him as "Ethel". I could not believe that they did not milk this scene for all it's worth; Nelson and Crane didn't even seem to notice the name at first. I was expecting them to at least look at each other and mouth "Ethel?"
Ethel is short for Francis Ethelbert Sharkey (Sharkey does not like his first name, either, one wonders what sort of relationship he had with his parents). Ethel and "Doc" (another childhood nickname?) had grown up together on the East Side. It's not surprising that Bradley would know Sharkey's hated middle name (his parents probably used the full address any time they were mad at him) but it is little short of incredible that Sharkey permitted Bradley to call him that without beating the stuffing out of him.
Any chance for some really good teasing gets lost when Kowalski spots a blip on sonar; it looks like another submarine. Bradley comments on this. They are supposed to be surrounded by picket ships to keep out all the riffraff while they attend to their mission, which, as it turns out, is to collect yet another superbomb capable of leveling half the planet. (Yet another would-be "deterrent device"--and we all know how well those work.) As they attempt to contact the unknown sub, 'Ski reports an undersea ship-to-air missile. (Polaris, if you look quick.) The plane is hit, but, unbelievably, the bomb does not go off. Patterson has calculated the approximate area where the bomb must have hit the ocean; and they head for it. Bradley warns them that the electrolytic action of the seawater will trigger off the bomb in four hours. (They really packaged the thing up nice and secure, didn't they?) Meanwhile, the enemy sub has disappeared from scope.
Bradley makes ready to go after the bomb; he will have to dive in 800 feet of water, using anti-compression oxygen (whatever the heck that is). Sharkey will assist. They spot the bomb in the water, and Bradley can apparently tell by looking at it that the bomb has already become activated. At this auspicious moment, the enemy sub pops up again. Crane orders Sparks to try and make contact (which seems like a pretty silly thing to do at this point). The sub is picked up on camera--they see the name VULCAN in nice bold letters. (Seaview has no such visible labelling, but then, when you're one of a kind, you don't need 'em.) There is no known listing for a submarine of that name anywhere. Vulcan opens fire on them. The third salvo causes some damage in the Missile Room, and after the fourth, they find that the torpedo firing mechanisms have burned out, as well as sonar and hydrophones.
More or less helpless, but needing to deal with that bomb, Nelson orders that the Flying Sub be launched, both to locate the enemy sub and serve as a decoy. On the Vulcan, we learn that the man in charge of the mission, Vadim, plans to capture the Seaview after he confiscates the bomb. Crane and Kowalski go out in the FS1, Nelson cautioning them that they have no heavy weapons. (Well, it used to be no weapons, but what happened to the laser system used in "The Menfish"?) FS1 apparently isn't the classified secret it used to be; Vadim casually identifies it, without even looking closely, as "a flying sub". He thinks it will come in handy when they locate the bomb.
Seaview has managed to get the hydrophones working again, and they learn that the decoy is working. Crane puts the FS1 in a search pattern, pretending to look for the bomb. Crane and Kowalski spell out to the audience that they will risk their lives to attack the Vulcan if it starts going after the Seaview.
Seaview locates the bomb again. We learn that Doc and Ethel used to go diving in the East River, searching for scrap that they could sell. This will be a trifle different. Bradley points out that the bomb has three "deterrent devices". Out in the water, Bradley states that the bomb has been activated (apparently he forgot that he had already noted that fact). No telling how much time they have (although I should think Nelson could calculate it if he put his mind to it.)
Vadim learns that they have been decoyed. Not through deduction; he receives a signal from his agent on board the Seaview--a signal that was set off when they located the bomb. It's exasperatingly obvious who the agent must be. Not wanting to waste more time, Vadim immediately orders that a laser be fired at the FS1. Crane notes that the Vulcan has gone to flank speed, and realizes that they've been found out. He attempts to stall for more time, but they're hit by the laser at 250 yards. Although they're both strapped into their seats, they promptly lose conciousness, while FS1 fetches up against (yes, again) that familiar chunk of rock.
In the process of deactivating the bomb, it tips and pins Bradley beneath it, and the lighting indicates that it's about to go off. Sharkey manages to partially deactivate it. Nelson sends down hoist gear, and they haul the bomb up to the Seaview. Inside, they have lost track of the FS1, but they note that the Vulcan has come to a dead stop right over FS1's last known position. Crane and Kowalski come to, but, as usual, the radio is dead. The Vulcan lands on top of them. Vulcan's helmsman must have an incredibly light touch; Crane thinks that it's the Seaview's diving bell that has landed on them. Preparing to leave the FS1, they're confronted with a gun. Zane, the commander of the Vulcan, brings them on board and introduces them to Vadim. "Ko-wal-ski" is pronounced "Kah-wul-ski", but 'Ski is too preoccupied to take offense. Vadim informs them that he is prepared to die (along with half the world, presumably) rather than let Seaview keep the bomb. Another signal from the agent indicates that Seaview is doing "something" with the bomb. Apparently the signals are not too precise--which is going to cause problems. There is no indication that Crane deduces the presence of a traitor--it would have been nice if they'd had him show some reaction. Crane and 'Ski are sent to the brig--but they don't go down without a fight.
Back on board, Bradley tells Nelson that the bomb has not been deactivated--they have two more detonators to defuse. (I'm wondering if someone got mixed up with "deterrent devices" and "detonators", because a deterrent device sounds like something to prevent anyone from approaching the bomb once it's activated.) At this tense moment, Chip Morton interrupts, calling for Nelson to come to the Control Room. Nelson irritatedly points out that he's in the middle of something, but Chip insists. Sharkey is detailed to assist Bradley instead.
Chip confronts Nelson with two problems: Vulcan is approaching at flank speed, and Sparks has been picking up a strange frequency, activated when they brought the bomb on board. Because the frequency is acting as a homing signal, any anti-tracking measures Seaview attempts will be useless. Rather than considering the possibility of an enemy on board, Nelson speculates that Vulcan had somehow managed to plant a homing device on board. He overlooks how conveniently it turned on just when it needed to. Sparks is unable to jam the frequency due to lack of time, and they're still working to repair the Missile Room circuitry. Having no other options at the moment, Nelson calls up the Vulcan.
Vulcan looks like a pretty decent submarine, but she lacks a radio shack; Vadim simply picks up a microphone from one of the control panels. Nelson tries to tell Vadim that the bomb is activated, but Vadim sees this as a mere play for time. Nelson pleads that it's going to go off in 15 minutes (don't recall anyone calculating that). Vadim pretends that he will give them 15 minutes--and then orders Zane to fire when they are 500 feet from Seaview. Seaview lurches violently, scrapes against an outcropping of rock (for the third or fourth time in as many episodes; I know Allen was a thrifty man, but this is getting ridiculous) and rams into the seabed. The bomb gets tipped over, but doesn't go off. (Well, it survived a plane exploding; a Seaview lurch is small potatoes.)
Sharkey finds the defusing tool where it had been knocked across the room--it has opened, and some circuitry is showing. Bradley claims that it's a neutralizer to prevent the detonators from being set off by electronic impulses. (This actually sounds quite reasonable, if we didn't already know better.) Sharkey deactivates "something"--at any rate, the ticking slows down and Bradley states that they have bought an additional 22 minutes. Seaview has sustained more damage; the power is out in the engines, and the reactor controls have been damaged. Battle stations are called, as they prepare to repel boarders. Sparks has now made a guesstimate on the location of the frequency signal--it seems to be coming from the Missile Room. With a dawning look on his face, Nelson dives out of the Control Room.
Vulcan is hovering 100 feet above the crippled Seaview. Bradley says that they still have two detonators to defuse (so what the heck did Sharkey do? Hit the snooze button?) They now have 18 minutes. Nelson orders a search for the homing device. If they had had more suspects on board, this would have been the moment when the truth became clear to the audience, just by looking at Bradley's expression.
Back in the Vulcan's brig (and it sure seems like a long time since we've seen them) Crane and 'Ski are contemplating a difficult escape. There's no way out except through the door; therefore the door it is. Crane extends an invitation to come in by smashing open a steam pipe.
Meanwhile, Nelson (not showing much finesse) reaches inside the bomb and yanks the second detonator loose. He grabs the defusing tool--and pauses, noticing something odd. Perhaps it was the weight, or the vibration of the circuits inside--or maybe he just got a close look at Bradley's face. Opening the tool, he finds the circuitry--only he knows that it's not a neutralizer. Sharkey only hesitates a moment before hauling Bradley up. Bradley's true colors start to show; he looks at Sharkey with a craven expression before Sharkey decks him. Aside from saying (twice) that he can't believe it, this is the only reaction Sharkey will show to the treachery of his childhood friend, the man that he suffered to call him "Ethel". I realize that, as Nelson said, there was no time to dwell it, but there was later, and he really should have shown something.
Back in the brig, 'Ski yells for help (but Crane doesn't; Captain's privilege, I guess). A crewman comes in, and is easily dealt with.
Bradley recovers from the punch--Crewman Ron spots this, and quickly signals the others to grab him. Sparks suddenly fly from the bomb. Bradley, who up to this moment has been reasonably calm dealing with the bomb, abruptly panics. Sharkey steps over and slaps him, but Nelson simply works faster.
Crane and 'Ski take out another guard, 'Ski hitting him so hard that he knocks himself down. They slip into the Armory, where they can surely find something to play with. A crewman comes in, and manages to yell for help, bringing a second crewman. There's a fairly prolonged fight sequence (well done except for the matter of two heavy-looking missile caps bouncing lightly off Crane and a crewman). It ends with Crane clutching an activated grenade. 'Ski finds the pin. Normally, in cases like this, you stick the pin back in and everyone sighs with relief, but 'Ski points out the nasty possibility that replacing the pin will not secure the grenade. Crane opts to toss the grenade out in the corridor, just in case. Nothing happens. Crane and 'Ski collect gas masks and gas grenades. They plan to cause a little chaos as they take their leave.
Vadim still doesn't believe that the bomb is activated, and Nelson doesn't think to have Bradley confirm it. Vadim threatens to kill Crane and 'Ski (in spite of only hearing Zane's version of the name, he pronounces Kowalski correctly). Finding that enough repairs have been made to launch missiles manually, Nelson orders a torpedo aimed at the Vulcan--knowing what it will mean. Chip hesitates, and Nelson blows up at him. (He's under a strain; we'll make allowances.)
Crane and Kowalski invade the Vulcan's Control Room and toss their gas grenades. Zane manages to wound 'Ski before Crane shoots him. They rush to find scuba gear.
Seaview makes a direct hit on the Vulcan. The resulting concussion (which probably should have killed Crane and 'Ski) causes Seaview to lurch, knocking everyone down. The bomb rolls against Bradley. This same bomb had merely pinned him earlier; this time it kills him. Why they always have to kill off the bad guy, I don't know. Haven't they heard of jails? The bomb starts smoking. Nelson jams his hand inside the bomb again, and yanks out the final detonator. Sharkey stolidly announces Bradley's death. Nelson orders a search begun for Crane and Kowalski, but it's unnecessary; Crane has assisted the wounded 'Ski back home, and they're outside waiting to be invited in.
Quite a tense episode, with the action bouncing back and forth like a tennis ball, but there should have been more suspects to keep us guessing a while, and even if Irwin Allen didn't approve of personal dramatics, Sharkey should have been allowed some more reaction.