What do the stars of the “Universal Soldier” film series have in common with “Brokeback Mountain” cowboys?

Jean-Claude Van Damme, the onetime “Muscles from Brussels,” and Dolph Lundgren, the “Siberian (Stockholm, actually) Express,” just can’t quit each other.

They reunite yet again for “Black Water,” an oddly over-plotted and implausible action pic starring a couple of wizened action stars who peaked in the ’90s.

The intervening years have seen not just Z-movies, but something resembling “comebacks” for these two — “JVCD” and reality TV for Van Damme,  “Expendables” and “Sharknado” outings for Lundgren.

Like their contemporaries, Sly, Arnold, Bruce and Mel, they’re beating back Father Time, or trying to. Their head-busting’s been replaced by gunfighting.  The scripts they’re forced to shoot? As awful as ever.

Van Damme plays Scott Wheeler, a spy or agent of some sort who wakes in a featureless prison cell. He shouts into the void, “Where the Hell AM I?”

A voice, a fellow “inmate,” we come to understand, replies that “officially, it doesn’t exist…Neither do you.”

That would be Marco (Lundgren), a man of certain skills with “a terminal case of ‘I know too much,” similarly “disappeared” into the void.

Wheeler, at the urging of Marco, thinks back to the “last thing” he remembers. Flashbacks take us to New Orleans, an assignment of some sort gone wrong, the dishy contact (Courtney B. Turk) half his age who Bond Babed her way into his bed right before everything went wrong.

Now, mysterious competing government agencies, repped by Ferris (Patrick Kilpatrick) and Rhodes (Al Sapienza) are competing to see who gets to torture our hard target.

“Guys like him have an infinite threshold for pain,” Ferris growls, upping the ante. “You want a man to tell the truth? Put a needle in his eye.”

That’s kind of twisted, if you know JCVD’s history. He was successfully sued in the ’90s for half-blinding a stunt man in a fight scene gone wrong in “Cyborg.” Penance?

Somehow, Wheeler’s got to get the drop on his captors and start the long process of a prison break — one complicated by the film’s title. No “Black Water” isn’t a play on a former U.S. government contractor, but the conditions of their imprisonment.

Much of the movie, our two heroes are separated — one, making new allies, killing old enemies, working his way through this “facility” until, of course, he gets back tto the long-absent Marco.

Because of that whole “can’t quit you” thing.

Part of Van Damme’s appeal has always been the mismatch of seeing someone his height fight a world of villains and evil minions, always much larger. A little of the fun of pairing him with Lundgren once was that height mismatch, a sight gag that many a comic duo have exploited. Nothing is made of that here.

There is a Van Damme offspring in the supporting cast. See if you can spot him.

The most interesting scenes in “Black Water” are those first moments of mystery, harking back to Pirandello or that classic “Twilight Zone” episode, “Five Characters in Search of an Exit.” The mystery is far more interesting than its solution. The actors, with their gruff history — more history than real chemistry — less interesting than their confused characters.

Letting Wheeler and Marco reason out their plight, with less specific flashbacks not ALL focusing on Van Damme’s Wheeler, would have heightened the mystery, still leaving time for the two or three memorable one-liners, and time for shooting butts and taking names.

What all involved, including cinematographer-turned-director Pasha Patriki, settle for is easier, dumber and far less interesting, a movie that lives down to its vague, murky title with endless shootouts through sets that don’t remotely resemble what this prison is supposed to be.

As for the performances, Van Damme and Lundgren may not be able to quit allowing producers to pair them up. But they should. Movies like this and their work in them isn’t doing either of them any favors.

MPAA Rating: R for violence and language

Cast: Jean Claude Van Damme, Dolph Lundgren, Jasmine Waltz, Patrick Kilpatrick, Al Sapienza

Credits: Directed by Pasha Patriki, script by Chad Law. A Saban Films release.

Running time: 1:44