PHOTO COURTESY SONY PICTURES / CTMG INC.

It is difficult to explain why “Madame Web” is as bad as it is. I could tell you about the individual absurd moments, which are legion, or quote particularly insipid lines from the insufferable script. I could point out the innumerable plot holes, which are so vast they can no longer accurately be called holes; they’re more plot voids.

But the film’s unique decrepitude is cumulative. The individual badness of these many, many flaws is notable, but not exceptional; plenty of movies have bad lines and nonsensical plot developments. But “Madame Web” stands alone in that it never manages any counterpoint to these failures; there is not a good stretch, a compelling arc or an intriguing development to offset all of those inanities.

It’s bad. It never gets any better. Then you go home. That’s the whole experience.

If you manage to stay alert and attentive from beginning to end — and trust me, you won’t — you’ll scratch your head through a thin story of arachnid destiny. Cassie Webb (Dakota Johnson) was born in a cave in the Amazon, with a tribe of superpowered spider-people serving as midwives; her mother, a researcher, died in childbirth after a generic bad guy (Tahar Rahim) shot her to steal a rare spider.

I’ll give you a minute to work out the details in the preceding sentence. Actually, don’t — they won’t make more sense no matter how long you think about them.

After a near-death experience, Webb begins seeing fractured visions of the future. When they show that the same underwritten villain who killed her mother is planning to kill a trio of unassuming teenagers, she reluctantly lurches into action.

There’s very little action in “Madame Web,” as most of the runtime is spent hiding from the villain or seeking answers about Webb’s headache-inducing visions. When it is time for a daring rescue, our hero drives through a wall and hits the bad guy with a car, in a sequence that plays out like a hastily edited “SNL” punchline.

This happens twice.

It must be said that Johnson provides some moments of joy, occasionally creating an endearing moment through sheer charm — and even throwing in a sarcastic eye roll or two, helpfully acknowledging that she knows this is a ridiculous endeavor. She’s good enough that “Madame Web” probably isn’t the worst superhero movie ever made.

That is, however, the best thing I can say about it: There are probably worse movies out there.

My Rating: 2/10

“Madame Web” is now playing in theaters.