LONDON - On-set interviews are a tricky job for any actor – particularly in the world of superhero movies, where many journalists have deep-rooted knowledge of the material and are duly hungry for information. Secrets must be kept, spoilers must be skirted, intrigue must be fed. The line between saying too much and too little is a fine one, and Chris Hemsworth seems well aware of this as he sits down to face a particularly inquisitive firing squad of film bloggers during the filming of “Thor: The Dark World” last October.

It's a damp, slate-gray day in London, and it's clearly been a long one for the 29-year-old Australian actor, who arrives at our makeshift interview tent in full costume, his somber battle gear and signature blond mane – duller and lanker, respectively, than what he sported in 2011's sleek, shiny “Thor” – caked in mud that may or may not have been part of the shooting plan. At a gym-built 6'3”, he's not significantly less imposing a presence than the hulking Norse god he's already played twice, to star-making effect, in “Thor” and last year's phenomenally successful superhero-salad blockbuster “The Avengers.”

So it's amusing to see this formidable figure forced to play coy. Resorting frequently to nervous chuckles and stammering “um” sounds, he politely fends off one question after another that demands a little too much inside knowledge of where Emmy-winning director Alan Taylor and his team are taking Thor for his second solo screen adventure.

Can he elaborate on the personal dynamic between Thor and newly arrived supervillain Malekith (played by Christopher Eccleston)? No, he can't: “They're obviously not related,” he says with a sheepish smile. Okay, what can he tell us about the developing relationship between Thor and buxom childhood friend Sif (played by a returning Jaimie Alexander)? “Um, not much!” he says, with a playful glint in his eye – he's doing the dance, and he knows it. “There’s obviously an attraction, and there was little, uh, peppering of that in the first one. There may be more indication this time.”

And so on and so forth, most revelations couched in maybes as Hemsworth teases us with good grace and scarcely suppressed excitement; whatever he's holding on to, he seems to think it's worth the wait. What can he tell us about “The Dark World,” though? Well, for starters, he can reveal something of the story world itself – dark or otherwise – which he claims is larger and more elaborately realized than in the first film. Does it maintain that film's balance between Earth and the realm of the gods?

“It’s certainly set in both worlds, pretty substantially,” he says. “We certainly see more of Asgard, and more of the nine realms in this film than we did in 'Thor.' In 'Thor,' we were just on Asgard, whereas this time there’s a bigger universe out there which we get to explore ... The scope of this just feels massive, you know. I mean, we were just in Iceland for a week, and there’s volcanic lava, rock mountains and snowcapped mountains. We didn’t see that in the first one. So it already feels like there’s a bigger expanse to it.”

He partially attributes the shift in the film's story world to the presence of new director Taylor, who took over from Oscar nominee Kenneth Branagh – an unexpected choice to direct 'Thor' in the first place. Branagh is a renowned classicist, whose Shakespearean background infused the first film with a literate sense of humor and heightened dramatic register. Taylor, by contrast, is best known for his work on such renowned TV shows as “Mad Men,” “The Sopranos” and “Game of Thrones,” and apparently prefers a shot of realism (inasmuch as it exists) in his superhero movies.

“Obviously with two different people you get two completely different styles,” he says. “But they're also two very different stories: an origin story versus the ongoing story … Thor’s journey, I think, picks more so up from where we left the first one. About to take on the throne, about to earn the right to be king. And now coming to the realization of what responsibility comes with that.

Guy Lodge is a South African-born critic and sometime screenwriter. In addition to his work at In Contention, he is a freelance contributor to Variety, Time Out, Empire and The Guardian. He lives well beyond his means in London.