'Maze Runner: The Death Cure`` is 144 minutes that you can never get back

So things really aren't going well, not one bit. The apocalypse has more or less happened -- or worse, it's in the process of happening. There's a virus going around, and three-quarters of the people on Earth are infected. Most cities are destroyed.

Oh, yes, and about that virus? It turns people into zombies -- not literally, in a textbook definition sense, but zombie-like: A lust for flesh, poor dental hygiene, a tendency to attack in packs, and to walk funny, have jerky movements and to show a certain exuberance in destruction. This is the world of ''Maze Runner: The Death Cure,`` the third installment in the ''Maze Runner`` trilogy, a kind of destitute man's impoverished cousin's answer to the ''Divergent`` series.

The first scene sets the tone, with its subtle blend of energy and fabulous stupidity. A team of young rebels interrupt a government transport. Apparently, one of their group, a young man named Minho (Ki Hong Lee), has been captured and is being taken to the last remaining city. And so, in a fairly exciting sequence -- albeit one that depends on not a single government agent being able to shoot straight -- the rebels disengage Minho's train car and, using a hooked cable and an airplane, lift it into the sky and transport it to their base.

Just one problem: They steal the wrong train car. Oops.

Though ''The Maze Runner: The Death Cure`` lasts a full 142 minutes -- every one of which, having spent, you can never get back -- the situation it describes is a fairly simple one. The non-zombie contingent of the human race is dying out, and the remaining authorities are desperate to find someone whose blood is naturally resistant to the contagion so they are kidnapping likely candidates and bringing them to the city center for experiments in the hope of creating a vaccine. That entire train transport, for example, was full of young people being forcibly brought to the city for experimentation.

You'd think that screening people for the anti-virus would be a pretty straightforward process, but no. Instead, for reasons that are never explained, each person is tortured, strapped into a machine and forced to endure horrible and terrifying hallucinations. Understandably, the rebels want to rescue these young people from state sponsored torture.

All this creates a rather odd situation for an action movie, in that neither side has a monopoly on virtue. The authorities want to barricade themselves against the zombies, but that's not so different from what the rebels want, to establish a cozy little colony of people immune or uninfected. Also, at least the government is looking for a cure. The rebels are trying to disrupt the research.

Yet there's really little point in investing more thought in this movie than the filmmakers, is there? ''Maze Runner: The Death Cure`` was not intended as something to contemplate, but as a moment-by-moment proposition, and scene by scene, it's not horrible. It's not even boring. Led by a reasonably engaging cast -- Dylan O'Brien as the rebel leader, Kaya Scodelario as a young researcher -- this third installment gently swings from scenes that are mildly disappointing to others that are mildly diverting.

That doesn't constitute a recommendation, but rather expresses just a certain relief that it could have been worse. Not much worse, but worse.

Mick LaSalle is The San Francisco Chronicle's movie crtic.

Maze Runner: The Death Cure

2 stars out of 4 stars Science Fiction. Starring Kaya Scodelario and Dylan O'Brien. Directed by Wes Ball. (PG-13. 142 minutes.)