As August temperatures swelter on, the banal “Bullet Train” offers an excuse to hit the theater for some arctic-level air conditioning.

That sweet relief from the heat is just about all the film is good for.

The fast-paced, quick-witted, Brad Pitt-starring flick features a paper-thin but exciting plot, two-dimensional, goofy characters, quirky cameos, and buckets of blood and gore to keep things sufficiently fun, all without an abundance of storytelling depth requiring too much attention.

Pitt anchors the ragtag cast as Ladybug, a habitually unlucky snatch-and-grab guy who has been hired to steal a briefcase from the bullet train running from Tokyo to Kyoto, Japan.

While the job seems simple, Ladybug’s task will prove to be anything but. He encounters other hired guns, assassins and all-around bad guys, all on the same train, all tasked with different jobs.

These baddies include Lemon and Tangerine (Brian Tyree Henry and Aaron Taylor-Johnson), who’ve been hired to bring the no-goodnik son (Logan Lerman) of a shadowy crime boss home again. Then there’s Wolf (Benito Antonio Martinez Ocasio, aka Bad Bunny), who’s avenging the deaths of his entire wedding party, Kimura (Andrew Koji), who is looking for the one responsible for pushing his son off a building, and Prince (Joey King), who did the pushing.

As the train speeds towards its destination, each stop becomes more dangerous for our cast of characters, and their attempts at completing their jobs go further and further off the rails.

Based on the 2010 Japanese novel by Kotaro Isaka, the film alters the characters slightly, making them more cosmopolitan, and in the process, whitewashes more than a few. However, as the book’s author said in a New York Times article last month, since the character’s ethnicities are never explicitly stated, the casting could include white A-Listers like Pitt and thus reach a broader audience.

Tasked with adapting Isaka’s book was Zak Olkewicz, who leans incredibly heavily on witty banter as the main structure of the script. Though Olkewicz is not alone in this tactic — many dark action-comedies have sone the same lately — he worries less about character depth or backstories, no matter how tragic (there is one brief exception to this, but the majority of the film’s plot remains thin) and thins out any well-rounded story you may hope for. Intermixed with the quips are heavy helpings of exposition, just to make sure the audience is never lost on this midnight train to Kyoto. Surprisingly, though, most of it is well-written enough that the doses of backstory and flashbacks flow well and are funny enough to keep the pace up.

Director David Leitch keeps those high stakes moving along, and the film never feels its length. But given the spatial constraints of the story taking place on the eponymous train (save for those expository flashbacks), it maintains a repetitive beat structure that hinders the film from building as it should toward its explosive climax.

One of the more redemptive elements of “Bullet Train” is its generally funny cast. Pitt, Henry, Taylor-Johnson and Koji in particular shine in their respective roles given how little they have to work with. King, unfortunately, never quite rises to their same caliber, in part due to her rough time with the British accent and her character’s formulaic underwriting.

“Bullet Train” aims to be a wild ride of a summer popcorn-muncher, and it succeeds in that, but once it pulls into its station, the audience is left with little to make it a regular commute. Beyond the splashes of blood and largely forgettable jokes, it’s only really good for a one-way ticket to a few easy laughs and a cool evening out.

On screens this week: It’s 30-something going on 65 when a woman wakes to find herself aged over 30 years in “Mack & Rita.” Anime glam-rock musical “Inu-Oh” rocks onto the big screen. On Netflix, Jamie Foxx hunts vampires in “Day Shift” and the coming-of-age Broadway adaptation “13: The Musical” both drop Aug. 12. Owen Wilson plays a superhero whose headquarters are discovered by a pre-teen in “Secret Headquarters” on Paramount+. And for Marvel fans, “She-Hulk: Attorney at Law” premieres on Disney+ Aug. 18 and will stream new episodes weekly.

“Bullet Train”

126 minutes

Rated R for strong and bloody violence, pervasive language and brief sexuality.

2.5 stars