“Tropic” is tale of brotherly bonds sorely tested by an “accident,” set against their schooling for a competition to see who is fittest to be among France’s long-mission space colonists.

The latest by director and co-writer Edouard Salier (“Cabeza Madre”) is an incomplete allegory told in the fashion of the late period French New Wave. Think “Last Year in Marienbad” meets “THX-1138” — obscurant, with detours, puzzling character digressions, needless “chapter” headings and a Big Idea that maybe isn’t as big as everyone thought going in.

Tristan and Làzaro are twins and also friendly rivals in their Euro Space Camp/University, prepping to be among the elite chosen for the decades-long “Eternity” missions France and Europe have planned to compete with China, Russia and the US in space colonization.

They undergo a rigorous education in science and philosophy. The physical tests are straight out of “The Right Stuff” era NASA — including epic who-can-hold-his/her-breath-the-longest trials in the school pool.

“They’ll pick us both,” the cocky, outgoing Tristan (Louis Peres) declares (n French with English subtitles). Smart but bullied Làzaro (Pablo Cobo) isn’t as sure.

When their cruelest challenge faces them, it won’t come from the thuggish rival Louis (Marvin Dubart). A midnight swim at an off-campus lake coincides with some sort of meteor/space junk “event” that crashes in the water. Tristan, testing his shocking skills at holding his breath, is injured physically — boil-like scars and tumors — and cognitively. He’s “not the same” as before.

Their crushed Spanish single mom (Marta Nieto) endures andTristan moves from the space academy to the “special needs” school next door. Làzaro must soldier on. But even out of his brother’s shadow and missing his gravitational pull, he struggles.

Everything in a movie is invented for the story and supposedly included for a reason. But a lot of what Salier contrives for this five act drama sits on the fence between puzzling and pointless.

The whole “dumb school” next door gimmick is odd, a convenient way to keep the siblings close even after their paths diverge. So what the hell is the point of giving Tristan a girlfriend from there, early on, and then forgetting her?

Wandering among the kids he is associated with (“friends” seems an absurd stretch) after Tristan’s accident may be the most random plot point in “Tropic.” Do we need to hear a learning-disabled kid’s rap to see how far Tristan has “fallen?”

The script establishes Tristan as the “alpha” of these twins, aggressive, competitive and reckless. That sets up Làzaro to cruelly try and get him “back” by treating his now Phantom-of-the-Opera-masked sibling as if he’s still “in there.”

Truthfully, the whole “green glow (fluid) accident” feels contrived and half-baked, a kind of red herring in a movie that promises science fiction and delivers too little that really fits that description.

The acting is good, the production design properly austere and the tone chilly and meditative. There’s something here about spaceflight drilling the humanity out of its candidates, with Làzaro clinging to his as he maintains that brotherly bond.

But there just isn’t enough going on, enough to chew on or entertain, to make “Tropic” — remember the European Space Agency launches from tropical French Guyana — worth one’s time.

Rating: unrated, violence, profanity

Cast: Pablo Cobo, Louis Peres, Marta Nieto, Alane Delhaye and
Marvin Dubart

Credits: Directed by Edouard Salier, scripted by  Edouard Salier and Mauricio Carrasco. A Dark Star release.

Running time: 1:48