What does Thanos want?

That question lies at the heart of "Avengers: Infinity War," the at-once dark, maddeningly open-ended yet fiercely entertaining new chapter in the Marvel Cinematic Universe (MCU), which pits the titular global do-gooders - still scattered hither and yon after their 2016 falling-out with one another in "Captain America: Civil War" - against a cosmic villain who has been coyly signaling his evil intentions ever since the very first "Avengers" movie, in 2012. And that's without ever really appearing on-screen, except in teasing cameos.

Oh sure, everyone knows he wants the Infinity Stones. Or at least everyone who's been paying attention to the previous 18 MCU movies. Ever since 2008's "Iron Man," these interconnected installments have introduced audiences to the six gemlike "singularities": color-coded stones controlling power, space, time, mind, soul and reality. Taken collectively, these artifacts are the mother of all MacGuffins - plot devices that drive the narrative, but may or may not have much to do with the true message of the story.

But what does Thanos want with them? That question is answered, in a film that presents a villain in a more nuanced, complex (and arguably even sympathetic) way than most comic book movies do. That's especially unexpected, given that he's a purple alien (voiced by Josh Brolin), created from CGI motion-capture, with skin that looks like a cantaloupe.

What is not unexpected is the film's death toll. Fanboys and fangirls have already steeled themselves to the eventuality that favorite characters will die here. Opening with a distress call from the Asgardian refugee spaceship that was seen fleeing planetary destruction at the end of last year's "Thor: Ragnarok," "Infinity War" gets that outcome out of that way early, paving a path forward for a film that, while very funny for much of its 2-1/2-hour running time, ends on an almost stunningly somber note.

It should be mentioned that there is already a sequel planned for next year that is likely to act as a corrective - short of bringing people back from the grave. In the manner of the second and third "Matrix" films, and the "Deathly Hallows" segments of the Harry Potter films, you can expect that upcoming movie to be more of a conclusion to a giant, two-part saga - complete with this installment's cliffhanger ending - than a free-standing sequel.

Death and destruction, of course, is what Thanos has in mind.

"Infinity War" is big, blustery and brave, taking viewers to places that they may not be used to going. Whether Thanos ends up getting everything he wants is one thing. But audiences should be warned that they probably won't.

If you go

AVENGERS: INFINITY WAR

3 stars

PG-13, 149 minutes

Playing at Niantic, Mystic Luxury Cinemas, Waterford, Stonington, Westbrook, Lisbon