How do you screw up a “ticking clock thriller,” the surest among the sure-things in the action picture genre? You mess around with the “clock” too much, for starters.

In “96 Minutes,” set mostly aboard a couple of bullet trains in Taiwan, the timers on the bombs — you know, the cliched gadgets where all the suspense is in “Which wire do I cut?” — are decimal chonographs. They count down in 100 second increments.

Thus, every time a character says “How much time do we have?” and we can see “3649” on the LED display, another character blurts out “Just over an hour!”

But filmmakers Tzu-Hsuan Hung (director and co-writer), Yi-Fang Chen and Wan-Ju Yang don’t stop there. The clocks can be sped up or slowed down by our mad bomber’s design. If a train slows down (“Speed” style), the clocks speed up. If it speeds back up, the timer slows down, etc.

Whatever unspoken (in Mandarin or English) subtext the director of “The Scoundrels” and his co-writers were going for about physics, the nature of time, etc. (one character is a physics teacher) is unexplored and we sit and gape and wonder “How much longer does this trainwreck last?”

“96 Seconds” is about life and death dilemmas, self-sacrifice and choosing not to make a sacrifice and grief that takes the form of revenge. It opens with an event years past, pops into a “present” three years ago and skips forward to a current “present” when there are trains and bombs and flashback after flashback after flashback shows us characters “then” and now and a jumble of “personal” complications and motivations, enough to fill a season or two of your favorite soap opera.

At some point, my “not buying in” impulse curdled into “not buying any of this.”

Lee Lee-Zen of “The Pig, the Snake and the Pigeon” plays the leader of a bomb squad glimpsed in the film’s opening scene in TV coverage of train wreck. No, Jie Li isn’t handling the aftermath of a bombing. The story isn’t being told in one long flashback. That earlier accident is a “clue.”

Jie Li is then in charge of a crime scene — a bomb that’s been planted in a cinema some time later. Luckily, he’s evacuated the theater and he has his best bomb-defuser A-Ren (Po-Hung Lin of “Suffocating Love”) on the case.

He’s got the bomb-survival suit, the portable X-ray and the wire-cutters necessary. As long as he’s not distracted by the wedding to Det. Huang (Vivian Sung of “Taipei Suicide Story”) he can’t quite make himself plan.

But defusing this bomb means — a sinister voice on the cell-phone declares — that another one in a crowded department store will go off. The bomb squad has to decide to set off the bomb they’re working on, or defuse it and trigger the other.

That awful dilemma, a snap decision with horrific consequences, frames the movie.

Because three years later, survivors of that earlier tragedy are on board trains leaving a memorial service when the same multi-bomb scenario presents itself.

Didn’t the bomber die in the first blast? Aren’t the bomb squad folks “heroes?”

A-Ren quit the bomb squad, is finally ready to plan that wedding and resolve to never go to this memorial service again. Jie Li is now a captain who has to talk A-Ren back into action. As the former bomb defuser’s mother and cop-fiancée are on board his train, he’s got real motivation.

“As long as you live, nothing else matters.”

A physics teacher played by Bo-Chieh Wang (of “Eye of the Storm”) in a troubled marriage injects himself into the plot. Is that his wife (Yao Titi) on the other train, not taking his calls?

And what does the phantom bomber mean when he threatens cops who “don’t want your secret exposed?”

The picture’s convoluted plot and fluid grasp of time contribute to the leaden pacing this supposed pulse-pounding thriller suffers from.

There’s gravitas in some of the performances, with overly-theatrical flourishes in others.

Sentimentality and grief is grafted onto murderous revenge as peripheral characters’ motivations are introduced, muddied up and then somehow “excused” in the confusion of bombs, ringing cell phones and a tsunami of supporting players acted panicked.

One has a hard time investing in this or that possible outcome because the script waters down each scenario and keeps shoving — via timers that SPEED UP or SLOW DOWN — the climax further and further into the future.

And as you might guess, the climax is almost preordained to be chased by an anti-climax that doesn’t so much rewind the ticking clock as make us wish they’d gone analog from the start.

Rating: TV-14, violence

Cast: Po-Hung Lin, Vivian Sung, Bo-Chieh Wang, Lee Lee-Zen and Yao Yiti

Credits: Directed by
Tzu-Hsuan Hung, scripted by Yi-Fang Chen, Wan-Ju Yang and
Tzu-Hsuan Hung A Netflix release.

Running time: 1:56