“CAPTAIN AMERICA: CIVIL WAR” — 3½ stars — Chris Evans, Robert Downey Jr., Scarlett Johansson, Sebastian Stan, Anthony Mackie, Don Cheadle; PG-13 (extended sequences of violence, action and mayhem); in general release

Partway through a dramatic battle in “Captain America: Civil War,” a character makes a passing joke about 1980’s “The Empire Strikes Back.” It’s an appropriate reference, given that while “Civil War” maintains the high quality and fun factor that has become the Marvel standard, it is also the series’ darkest entry yet.

The chemistry of the Avengers superheroes has always whirred around the yin-yang dynamic of Steve “Captain America” Rogers (Chris Evans) and Tony “Iron Man” Stark (Robert Downey Jr.). And in “Civil War,” that dynamic is the focal point of the film’s conflict, though not quite in the way you might expect.

The film opens with a Rogers-led squad retrieving a bio-weapon from a group of terrorists in Nigeria. The Avengers save the day, as usual, but a miscue by Scarlet Witch (Elizabeth Olsen) winds up killing a dozen innocent bystanders.

Combined with the collateral damage of previous Avenger battles in New York, the District of Columbia, and Sokovia, world leaders decide enough is enough. Their solution is to make the Avengers directly accountable to the United Nations, replacing vigilante justice with controlled bureaucracy.

Stark feels especially guilty over the lives taken in his cross-fire, so he leads the charge to sign on the dotted line, and Black Widow (Scarlett Johansson), War Machine (Don Cheadle) and Vision (Paul Bettany) follow suit.

But Rogers is wary of the deal, fearful that bureaucratic red tape will keep the Avengers from doing their job, and along with Falcon (Anthony Mackie), Hawkeye (Jeremy Renner) and Scarlet Witch, refuses to sign.

It’s surprising to see Stark toeing the party line while Rogers resists authority, and their super-schism is tested almost immediately when a bombing outside the United Nations is pinned on Rogers’ old war-buddy-turned-super-assassin Bucky Barnes (Sebastian Stan), aka the Winter Soldier.

Stark is determined to bring Barnes to justice, but Rogers smells a rat, and their disagreement comes to blows at an airport free-for-all that brings Ant-Man (Paul Rudd) and Spider-Man (Tom Holland) into the action, as well as a mysterious new character called Black Panther (Chadwick Boseman), who has some personal motivations of his own.

The laundry list of superheroes is extensive even for Avengers standards, but directors Anthony Russo and Joe Russo wisely keep the focus on Rogers and Stark. Diehard fans might wish there was more screen time for individual favorites — “Civil War” will create lots of buzz for young Holland’s new Spider-Man — but to delve too much into fan service would make a complicated movie into a complicated mess.

But characters aren’t the only element the Russo brothers balance well here. “Civil War” starts with a bang and features numerous fantastic action sequences, but the flash is offset by genuine suspense and dramatic, tragic conflict.

Even better, “Civil War” never lets its heavy tone overwhelm the proceedings like Marvel’s comic competition over in the DC world have with movies such as this year’s “Batman v Superman.” There’s still plenty of humor and some genuine surprises (including two post-credits bonus scenes, so be prepared for the full 146-minute run time).

It isn’t a perfect effort — the battle at the airport is entertaining, but even the characters acknowledge that they are fighting at half-speed — but it’s plenty to reach summer blockbuster status, and “Civil War” will leave fans salivating for the next installment in the series.

It’s worth noting that while Robert Downey Jr.’s “Iron Man” standalone films started strong and faded fast, Chris Evans’ “Captain America” efforts have taken the opposite path. The Cap films are almost indistinguishable from the ensemble Avengers tent poles by now, and maybe that’s a big part of their success (though credit must be given to the impressive efforts of the Russo brothers). It also helps when your heroes aren’t just teaming up against a generic CGI monster for the third act.

But however you want to spin it, “Civil War” is another testament to the Marvel movie dynasty and hopefully a sign that fans are in for a fun summer at the theater.

“Captain America: Civil War” is rated PG-13 for extended sequences of violence, action and mayhem; running time: 146 minutes.

Joshua Terry is a freelance writer and photojournalist who appears weekly on "The KJZZ Movie Show" and also teaches English composition for Salt Lake Community College. Find him online at facebook.com/joshterryreviews.