Loki (Tom Hiddleston), left, steals some of his brother’s (Chris Hemsworth) thunder in the sequel “Thor: The Dark World.” (Jay Maidment)

Is “Thor” getting dumber, or am I?

I’m not referring to the Marvel superhero (Chris Hemsworth), a muscle-bound blond himbo whom no one has ever called a deep thinker, but to the movie franchise itself. With the release of “The Dark World,” the second film in the series about the hammer-wielding Norse god — or the third if you count “The Avengers” — I’m left with way more questions than I can answer.

For example, if Thor’s homeland of Asgard has the technology to defend itself from space invaders with long-range artillery and jet fighters, as we see in the film, why do Asgardian foot soldiers still run around with medieval swords and daggers?

And exactly how and when did the Bifrost get repaired? That magical bridge between Asgard and Earth was, as everyone knows, destroyed utterly at the end of the first film. It was still out of commission in “The Avengers,” leading the screenwriters to offer a bogus explanation for Thor’s appearance in New York City as the result of his father, Odin (Anthony Hopkins), pulling some strings. Huh? In the new film, the rainbow highway is suddenly good to go again, with no explanation.

Are Thor and his family divine or aren’t they? “We’re not gods,” Odin says to his son Loki (Tom Hiddleston) in what may be the biggest bombshell ever to drop in the MCU (Marvel Cinematic Universe). Oh really? Someone might want to tell creator Stan Lee, who has specifically referred to the Asgardians as divine beings.

But most important, why do the Dark Elves — the bad guys in “The Dark World” — look so much like angry Teletubbies?

Ow, my head.

“The Dark World” opens with Thor’s villainous brother, Loki, defeated and in chains; with Thor’s human girlfriend, Jane (Natalie Portman), pining for her absent lover; and with Thor preoccupied with stamping out uprisings on various of the nine realms that he and his kind rule over. So far so good.

But when Jane stumbles upon something called the Aether — a long-hidden source of destructive energy, which takes over her body like a virus — Thor must drop everything and return to Earth in order to protect her from Malekith (Christopher Eccleston). The evil leader of the Dark Elves, Malekith wants to use the Aether to — well, what exactly? Control the nine realms? Destroy them? Plunge them into darkness so he can harvest mushrooms?

Whatever it is, it isn’t good.

To be fair, there’s stuff to like in “The Dark World.” Loki, for example — whom Thor must reluctantly team with in his fight against the Dark Elves — is simply fabulous. Hiddleston steals the show here, making wickedness and treachery look a heck of a lot more fun than virtue. Cinematically, there’s also a great scene in which a flotilla of Asgardian funeral barges are lit afire with flaming arrows as they approach a waterfall. Sure, it’s probably entirely CGI, but it’s gorgeous all the same, especially in 3-D, and surprisingly moving.

In general, though, the action scenes are only okay. There is, however, one genuinely jaw-dropping bit of violence that startled me, especially for a comic-book movie.

Oh, and let’s not forget Odin’s facial hair. His white beard is magnificent, particularly the mustache, which wriggles down along the sides of his mouth in sinuous testimony to the skill of his Asgardian barber — or the film’s makeup department, which numbered 67 people. Odin may not be a god, but he has divine whiskers.

See? That’s the problem with “The Dark World.” If I’m spending that much time studying Odin’s grooming, there’s something wrong with the story, which is kind of slow to get going and features too many undeveloped threads.

What’s up with the jealousy, for instance, between the warrior Lady Sif (Jaimie Alexander) and Jane? After Thor brings Jane to Asgard, the two women shoot each other a couple of nasty looks. But otherwise the dynamic goes nowhere. Do something with it, or drop it.

There’s some humor, too, but far too little for my taste. This is especially disappointing after the first film, which made much of the culture shock experienced by contemporary earthlings who encounter a dude who drops out of the sky looking and talking like a Rennfest staffer who takes his job a little too seriously.

And that’s the real flaw with “The Dark World,” which seems to have inhaled a bit too much of its own noxious Aether. The only one who seems to have gotten the memo that the whole thing is a gas is the bad guy.

★ ★

PG-13. At area theaters. Contains action violence. In English and some Elvish, with subtitles.
112 minutes.