As moviegoers, we accept certain unalienable action-movie truths: Cars will blow up with one gunshot; bystanders don’t seem to mind multi-car pileups and a hail of gunfire will always miss our hero or heroine.

“Mission: Impossible III” is remarkable, because it actually manages to create some eye-rollingly implausible sequences. And I thought we wouldn’t notice it after all these years.

In “Mission,” Tom Cruise’s character, Ethan Hunt, is back working for the Impossible Mission Force to bring down an extremely dangerous black market honcho (played by the ever-wonderful Philip Seymour Hoffman.) After stepping out of the limelight to train agents, Hunt leaps back into action to save his woman and society. But a deeper, darker reason lurks: “Mission: Impossible II” made a lot of money.

So in the spirit of box-office bankability, Hunt and his ragtag crew storm the Vatican, race through the streets of Shanghai and stage a rescue in Berlin, all to obtain a very dangerous something-or-other marked as a biohazard. The mind-boggling complexity of the Brian De Palma original had an addictive appeal; this screenplay — written by three people, no less — covers up vapidity by throwing in some tinkling piano and a subplot about Hunt settling down and getting married and carries some insultingly obvious twists. It’s funny how people in movies don’t know the rules we all learn from the movies themselves.

Some of the scenes in the movie have an undeniably popcorn appeal, and Cruise is a fine action star as usual, but what kills “Mission” is its sheer preposterousness. A tape that self-destructs in 5 seconds is suitably hokey, but when the movie gets into voice and latex technology and the fact that no one notices agents scurrying around the clandestine Vatican, it breaks that unspoken agreement with its audience to at least make some sense.

This movie has no point, which is okay. Action movies don’t have to serve a higher moral purpose; if stuff blows up and we don’t get bored, thumbs up. But when the Oscar-winning Hoffman, one of the finest actors in the movies today, can’t even get enough screen time, something is wrong.