After an abrupt 9-month delay in order to convert the film to 3D (and, rumor has it, add more Channing Tatum), “G.I. Joe: Retaliation” is finally upon us. Would it surprise you to learn that “G.I. Joe: Retaliation” is complete nonsense? It shouldn’t. It really shouldn’t be surprising that a movie based on a television series meant to sell action figures has a half-baked plot and two-dimensional characters and masks them with misdirection in the form of a lot of explosions. Yet there are small kernels of a good movie in “G.I. Joe: Retaliation,” the first in the annual slew of fun but inconsequential summer action flicks.

The sequel picks up where the first left off, with Zartan (Arnold Vosloo) posing as the President of the United States following something known as the Nanomite Wars. It’s all gibberish as excuse for cartoonish action, but it’s not like you’re going to see a movie starring Dwayne “The Rock” Johnson for its nuanced take on global geopolitics.The G.I. Joes are framed by Zartan, and a strike on the team eliminates all but Roadblock (The Rock), Flint (D.J. Cotrona), and Lady Jaye (Adrianne Palicki). The survivors set out to find the reason why their government has betrayed them. Along the way, they recruit the help of mute ninja Snake Eyes (Ray Park) and retired General Joseph Colton (Bruce Willis), who is the reason they call themselves “Joes.”

The main problem with the film is that it seems unable to decide whether to be serious or cartoonish, and various actors fall on either side of the fence. The villains get to have more fun, it seems. Jonathan Pryce as Zartan impersonating the President delivers the line “I’m the quicker blower upper, baby!” with a particularly endearing B-movie zeal. Ray Stevenson as Firefly, whose weapon is actually robotic exploding fireflies, breaks into a prison with a motorcycle that literally splits apart into multiple live rockets. The doomsday device constructed by Cobra Commander is a satellite that drops a gigantic metal spike from orbit to trigger catastrophic seismic activity. It’s stupid and impractical and so, so stupid and kind of really great.

Elsewhere, a scene in which the retired Colton opens up every cabinet in his house to reveal a gun collection more extensive than that of any doomsday prepper strikes the ideal winking and exaggerated tone for the film—the four-digit combination on his gun locker is 1776. But the rest of the Joes don’t get to have nearly as much fun as their adversaries. Palicki has the unfortunate task of delivering a monologue about how Lady Jaye’s father did not respect women in the military while Flint (and by extension, the audience) voyeuristically watches her undress. She also has to say the line “We can mask our IP address. I’ll cyberblast an encoded beacon every six hours,” as if that means anything. In almost every scene, The Rock is one overzealous flex away from ripping out of his clothes.

Until the its climax, “G.I. Joe: Retaliation” feels like two separate films. Roadblock and crew’s recovery stateside has all the trappings of a generic, slightly jingoistic ‘80s action film, while a separate narrative shows Snake Eyes and his villainous counterpart Storm Shadow in a vague Asian setting referred to only as “the mountains.” Whereas the Roadblock arc is about bullets and explosions, the Snake Eyes storyline is more evocative of old martial arts B-movies, complete with a faux-philosophical, half-blind sensei played by RZA. It also provides the film’s most exciting action sequence, a ninja sword fight in which all involved swing along the side of a mountain.

Perhaps the greatest indication of the missed potential of “G.I. Joe: Retaliation” comes in two scenes at the beginning, in which The Rock and Channing Tatum’s Duke shoot the breeze in exchanges that feel largely improvised. Unfortunately, Tatum’s appearance amounts to an extended cameo, and for the rest of the film, The Rock has nobody to bounce dialogue off of. There is a distinct lack of chemistry between The Rock and the other actors, accented all the more by those couple of opening scenes that hint at what could have been.

If you have some time to kill, you could do worse than “G.I. Joe: Retaliation.” In between some competent action and a lot of techno-military nonsense, there is a ghost of a better movie here. Maybe the filmmakers know this. But knowing is only half the battle.

—Staff writer Brian Feldman can be reached at bfeldman@college.harvard.edu.