More than every Marvel Studios film before it, Avengers: Infinity War hits the ground running and doesn't stop for two and a half hours. It begins in medias res, immediately establishes dominance over the audience (and their heroes on screen) and barely gives you even a second to breathe.

It's the epitome of a summer blockbuster. The explosive action is practically nonstop, breaking only occasionally for jokes and a touch of romance — though without ever breaking its grim, apocalyptic tone.

But it comes with a caveat: This cannot be your first, second or even third Marvel movie. Even with its long running time, there is no room for backstory and little space for explanations. There is a lot of ground to cover, and the script trusts you to keep up.

Need to catch up before 'Avengers: Infinity War'? Here are the movies you can skip

As such, it would do little good for me to recap the story so far. Don't know who Vision is? Not sure what's up with the Guardians of the Galaxy? Did you not know that there is a sorcerer behind the scenes in New York casually twisting reality and turning back time? Then, frankly, Infinity War is just going to confuse and overwhelm you. It will give you a flashy spectacle, but you won't enjoy it the same way the longtime fans will — because they're going to love every twist and turn the movie takes.

Those fans will be in for plenty of surprises, but they won't always need them. The audience most fit for Infinity War will cheer the first time the wonderfully bearded Captain America shows up on screen, and its not like his appearance will catch them off-guard. Even the moments of pure pandering, of which there are a few, feel like rewards for sticking with the Marvel Cinematic Universe for 10 years and counting, and it's hard to begrudge the filmmakers that.

For as much as it's about its marquee superheroes (and there are well over a dozen of them), Infinity War revolves entirely around its villain, Thanos. He's been the behind-the-scenes Big Bad since the first Avengers movie, and he lives up to the fear he injects into creatures living across the galaxy. An incredibly powerful enemy who only gets stronger over the course of the movie, this purple behemoth is capable of swatting even the Hulk away like a fly, making you afraid for the lives of your favorite characters every time he enters the fray. His ultimate goal? Wipe out half of all life in the universe, which is, y'know, a lot of people.

Josh Brolin as Thanos

Josh Brolin as Thanos

/Marvel Studios via AP

While he's not the most relatable or grounded of Marvel villains, there are some moments when you might, for a brief second, understand why he's doing what he's doing. Sure, he's got issues, but the thing that drives him here makes for a better movie than the romantic obsession with death he had in the comics.

One of Infinity War's most impressive feats is that it doesn't collapse under the immense weight of its ambitions. Even when the plot is pulled in various directions, every scene is laser-focused on getting all the pieces on the board and lined up for the end game. What's more, the time the movie spends with each superhero in its arsenal has at least a small touch of that character's unique quirks. For instance, the scenes in Wakanda feel like a direct extension of Black Panther, while a battle involving Doctor Strange is appropriately weird.

This is helped by the smart pairing of characters at every turn. Take Iron Man and Doctor Strange, who are both brilliant, science-minded leaders who (of course) are going to clash. Likewise, the more lighthearted Thor and Star-Lord are able to swap stories about their deep familial issues while not getting too heavy about it. These meetings are why audiences come to the Avengers movies in the first place, and the key moments don't disappoint.

The part of Infinity War that will be most divisive (and most talked about) is how it ends. Despite moving away from calling this movie "Part One" and 2019's as-yet-untitled Avengers-4 "Part Two," Infinity War is definitely only the start of something massive. The story isn't over here. Based on where things are left, it's going to be a long, excruciating wait to find out what happens next.

Avengers: Infinity War (A-)

PG-13 (for intense sequences of sci-fi violence and action throughout, language and some crude references.) 149 minutes. In wide release.

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