The clock has run out on Ethan Hunt. Then again, Tom Cruise seems to do almost everything like he’s running out of time. After three decades and eight films, everything that star/producer Cruise has left on his “Mission: Impossible” bucket list comes down to this. Every jaw-dropping stunt, every unexplored location, every friend and foe, new and old, he has to fit it all into “Mission: Impossible – The Final Reckoning,” and like Ethan Hunt, he just might die trying. Cruise has one final message to impart with this series, and he’s hoping it won’t self-destruct in five seconds — it’s too important. That message is delivered by Ethan’s oldest friend, Luther (Ving Rhames), who reminds us in his velvety rumble that the future is not written, that we are the masters of our own fates. After nearly three hours of watching Tom Cruise try to murder an uncontrollable AI called the Entity, the message feels especially resonant in a time when everything feels hopeless.

Ethan will always “figure it out,” as he and his team repeat during “Final Reckoning.” He is but one man, but to save humanity he will plunge to the bottom of the freezing ocean; he will wrestle a plane to the ground with his bare hands. Ethan Hunt’s not giving up, are you?

Co-written by director Christopher McQuarrie and Eric Jendresen, “Final Reckoning” picks up where “Mission: Impossible – Dead Reckoning” left off, with Hunt and co. in a desperate bid to track down the source code of the Entity, the artificial intelligence unleashed by Gabriel (Esai Morales).

The world stands on the brink of total annihilation, as the Entity has infected the entire internet and now controls almost every nuclear weapon on the planet.

A doomsday cult has sprung up around this Entity, with the goal to eradicate humanity, and has infiltrated the highest levels of the armed forces. U.S. President Erika Sloane (Angela Bassett) stands with her finger on the button, though she trusts Ethan enough to grant him 72 hours to kill the damn thing himself.

The first hour of “Final Reckoning” proceeds at a breathless, breakneck pace, playing like another film’s third act climax. It’s a feat of editing by Eddie Hamilton, who has to toggle between flashbacks and exposition dumps delivered by a squadron of beloved character actors (Holt McCallany, Nick Offerman, Charles Parnell, Janet McTeer, Henry Czerny) and the familiar faces of Ethan’s ragtag team (Simon Pegg, Rhames, Hayley Atwell, Pom Klementieff, Greg Tarzan Davis).

McQuarrie and Jendresen have to go back to the beginning and make one significant stop along memory lane, connecting Ethan’s mission in the third film to this situation, in a reverse-engineering “butterfly effect” story. It emphasizes the burden of responsibility he feels, reminds us of the trauma that he’s suffered, and what motivates him to complete the mission (his loved ones).

It’s often sprawling and unwieldy; some characters are badly underwritten, others receive their overdue redemption. But in “Final Reckoning,” the plot and logistics have never been less important. They’ve got to put one doohickey together with another doohickey to kill the Entity, wipe out the internet and save humanity. But the busyness and noise of the frantically woven narrative connective tissue fades away when Cruise is doing what he does best: absolutely mind-boggling stunts, in which McQuarrie focuses on the visual storytelling and the emotional core of Ethan’s singular quest to save the world from itself.

Everything gets quiet during what might be the film’s most effectively executed sequence as Ethan goes swimming amongst torpedoes in a sunken Russian sub that’s also falling to the depths of the Bering Sea. Max Aruj and Alfie Godfrey’s score turns eerie and ancient; there’s a spiritual quality to the quest. (Also, we need a spinoff about the submarine that drops him off, piloted by a crew of stoic seamen, including standout Tramell Tillman, and Katy O’Brian and her shoulders.)

In another bravura sequence, McQuarrie and Cruise pay tribute to both Cruise’s other major action franchise, “Top Gun,” and early action cinema, as he takes to the skies, clinging to a biplane during a jaw-dropping dogfight.

It’s as if we’re watching an aerial stunt show, and calls to mind “Wings,” the 1927 World War I air combat movie that won the first best picture Academy Award.

These references to cinema history are an integral part of McQuarrie and Cruise’s message to reject modernity and embrace tradition, as Ethan battles the inhumane forces of artificial intelligence. Cruise wants to save us from ourselves through the magic of the movies, and he’s putting his body on the line in order to do so. It may be a futile fight, but that doesn’t mean he’s not going to do it anyway, with hope and optimism, and an inherent belief in the goodness of his people.

‘MISSION: IMPOSSIBLE – THE FINAL RECKONING’

■ 3.5 stars (out of 4)

■ MPA rating: PG-13 (for sequences of strong violence and action, bloody images, and brief language)

■ Running time: 2:49

■ How to watch: In theaters May 23