The teaser starts out in 1524, with a pirate galleon under fire and going down. Its captain, having ordered the others to abandon ship, stands boldly on deck (protected by a sheet of glass, on which you can see water dripping) prepared to go down with his ship. He lays a curse on his treasure, to last a thousand times a thousand years (which is a pretty darn long time).
Jump to 1978, and Admiral Nelson is instructing two teams of divers who are going to inspect the ocean's latest installment in deterrent weaponry. This time, it's an inter-continental defense system of 275 missiles (shortly whittled down to 274) linked by a massive cable system. An electronics specialist, Captain Brent, is on board as a consultant. Even if you didn't recognize the voice, you could guess at how the teaser would end by how carefully Brent remained with his back to the camera until the last moment. He is, of course, the spitting image of the 16th century pirate captain, right down to the scar on his cheek. (There will be a confusing twist on this later in the episode.) Albert Salmi is great in this role--he's very good with loud, hoarse-voiced fanatics, giving the impression of a man who yells and screams often enough to have damaged his vocal cords. Brent very seriously warns the divers that they are in a region known to have a lot of sunken pirate treasure, which is cursed. Nelson laughingly goes along with him. One team checks out missile # 147. Oddly, the buried silo clearly has two flaps which are meant to close over the missile inside, but they are open when the divers reach it.
Everything seems normal, but moments after one of the divers spots an old (but nice and shiny) doubloon in the sand, a strange pulse of energy travels along the cable and hits the missile. The warhead does not explode, but the damage rocks the nearby Seaview, as well as killing the divers, who had no chance to report the energy pulse. The explosion appears to have been caused by some unknown malfunction.
Brent has been giving a lot of significant looks to the audience, and when the mini-sub is prepared to launch and help investigate the mishap, he waylays one of the sub divers, Henderson (good name) and takes his place in the mini-sub.
Henderson is discovered badly wounded (but a lot better off than his partner will be). Nelson and Crane quickly deduce that Brent must have been responsible, although Morton neglects to mention that Brent had been asking a lot of questions about the mini-sub. They break into Brent's quarters, to find a large chest with glaringly fake giant coins (and how did he get that cumbersome thing onto the Seaview in the first place?) while behind them a giant Jolly Roger unrolls down the wall. This scene was a little ridiculous. They may try to give people as much privacy as possible on the sub, but there are various reasons why personnel might need to enter Brent's cabin, so why would he have all that stuff out in the open?
Nelson fires off a request for information on Alfred Brent. The answer is not promising. He and all his family have an excellent reputation, going back hundreds of years--except for a 16th century buccaneer. Interesting that a quick check on this man pulls up a genealogical record going back that far. Even more hard to believe is the notion that the family only had one black sheep in all that time.
Brent makes contact with the Seaview, babbling wildly about treasure and gold everywhere. Ominously, there is no sound or mention of the second man on the mini-sub. Brent suddenly screams that something is coming at them, and there is an explosion. Seaview, of course, lurches in reaction to the shock wave, which they then determine came from about 40-45 miles away--near an island that was a known hang-out for pirates in the 16th century.
Crane and Kowalski take off in the Flying Sub to investigate. Kowalski is concerned about all the strange goings-on. Crane assures him that they are on a standard mission, that just happened to have a couple of accidents. It's no surprise to the viewer that immediately after the words leave Crane's mouth, they are confronted by what looks like a old-style pirate galleon--and they promptly come under fire and hit the drink, fetching up against a familiar-looking rock on the sea bed.
Crane suits up and heads for the island, leaving Kowalski the task of repairing the Flying Sub and getting back to the Seaview. Crane is confronted by Captain Brent, all rigged out in conventional pirate attire, and accompanied by henchmen in similar dress.
Kowalski makes it back to the Seaview, and Nelson gets a new report on Brent. Brent's birth certificate has been forged, meaning that he's not an actual member of that fine family, meaning that he's not actually the descendant of that 16th century buccaneer...so how is it that he looks like him? Or was the first part of the teaser a complete fantasy? All these matters make it plain that something is seriously off-kilter...only the Powers That Be, in the shape of Admiral Howard, refuse to acknowledge it. He insists that the defense system be hooked up right on schedule. Nelson accepts the order...and promptly turns command over to Morton and undertakes to do his duty as he sees it. Chip doesn't look too happy at the prospect of explaining his Admiral's desertion to the authorities.
The situation gets increasingly bizarre. They could have made an interesting contrast of the old buccaneers with modern-day piracy, but instead we have a group of men, for no good reason, running about like a bunch of little boys playing pirate. As I said, it was colorful and entertaining to watch--but ludicrous. Brent may have convinced himself that he's the reincarnation of an old pirate (and quite possibly having forgotten about that forged birth certificate) but what about the rest of his men? Wouldn't they have thought Brent was crazy? Or did they like the idea of letting loose the child within and playing dress-up? (I was wondering if Mr. Sebastian really needed that eye patch, or if Brent hired him for his team because of it.)
Brent manages for a second time to knock down the Flying Sub, although this time, forewarned, Nelson has a defensive shield in place that absorbs most of the impact. A bit shaken up, Nelson and Kowalski proceed to investigate.
There's a tense, sadistic little scene where Crane is chained to a wall and left to the tender mercies of Mr. Sebastian, who has a flair for flame. Crane faces the threat of imminent torture with admirable calm (that's why he's the Captain), waits his chance, and knocks Sebastian down and out with a well-placed kick. Getting loose, he retrieves his scuba gear, and then (intentionally or not) follows the recovered Sebastian straight to Brent's underwater base. He finds the pirates, still all dressed up and bellowing in accepted pirate fashion, working in an ultra-modern tech center. Brent somehow learns that Crane is in the vicinity (don't know how, unless Sebastian quietly called him before sneaking up on Crane), and, of course, cannot resist informing Crane of what is going on. He's going to destroy the defense system (and a sizeable portion of the Western Hemisphere) on behalf of an unnamed country, in exchange for unrestricted access to the vast amounts of old pirate loot in the vicinity. His ancient pirate galleon, La Reina Isabella, is simply the projection of a small replica, combined with modern electronic weaponry.
Nelson has meanwhile managed to patch into the cable that Brent had patched in to the main defensive cable. When Brent sends his power burst along the cable to ignite the defense system, they play a kind of reverse tug-of-war, pushing the electrical burst back and forth, until the small Flying Sub manages to shove it clear back to Brent's base. When sparks start to fly, Crane sensibly elects to get the heck out there, tossing Sebastian over the rail and running for the escape hatch. The resulting explosion somehow does not affect him much, and he locates the Flying Sub (or they locate him) and they head for home.
Admiral Howard conveniently forgets that he had not thought Brent worth looking into, so of course he cannot charge Nelson with dereliction of duty for having done so. Nelson and Crane both look as though they're amused at having put one over on the Powers That Be. Nelson shows off a coin trick, using a doubloon that perhaps Kowalski found while connecting the cable--proving that Nelson is not concerned with old curses.