There’s plenty of running in "Maze Runner: The Scorch Trials," as the movie’s teen heroes, survivors of last year’s surprise hit "The Maze Runner," hurtle from one spectacular crisis to another and another and … If you can lose yourself in the eye-popping set pieces, and don’t expect much in the way of character development (or dialogue), you may conclude that it’s OK as a sci-fi action sequel.

"Scorch Trials" begins exactly where its dystopian predecessor ended, as teenagers Thomas (Dylan O’Brien), Teresa (Kaya Scodelario) and others escape from the maze constructed by a mysterious agency known by its acronym WCKD, which unsurprisingly is pronounced "wicked." WCKD is working to cure a virus that has wiped out much of the human race, turning some survivors into a particularly malevolent kind of zombies.

The youngsters are taken by soldiers to a highly secured military base and research station, where they encounter other veterans of the maze. Thomas is convinced by a troubled teen named Aris (Jacob Lofland) that something’s rotten in the facility, which sets the stage for a breakout.

The young people emerge into the Scorch, a brutal desert landscape that offers a wide assortment of dangers — including zombies and WCKD’s minions. But there are rumored to be survivors who have avoided the zombie plague, and there may be an army of good guys out there somewhere.

Among the many adventures that follow, our heroes stumble into the lair of a sort of "Mad Max" group of survivors led by the ruthless Jorge (Giancarlo Esposito, relishing the role), who thinks he might be able to sell the young people back to WCKD for a nice profit. Another scene, totally out of nowhere, throws Thomas and company into a decadent and druggy party scene. Catnip for the film’s target audience? Only director Wes Ball knows for sure.

Can WCKD be stopped? And how does villainess Patricia Clarkson keep her togs so dazzlingly white? Well, a third "Maze Runner" film is due out in 2017.

Ball has a talent for the action sequences, but the dialogue, by T.S. Nowlin (based on a James Dashner novel), rarely rises above pedestrian. There’s lots of eye candy, and the pace is fast, but somehow the movie falls short. You’re forgiven if you get the idea that "Scorch Trials" suffers from "middle movie" fatigue.

Review by Walter Addiego, San Francisco Chronicle