Why’d they have to do Indy like that.

“Indiana Jones and the Dial of Destiny” is the fifth and final installment of the beloved franchise that revolutionized action filmmaking through a retro lens back in 1981 —and it is the absolute worst chapter in the series. Clocking in at a bloated two hours and 24 minutes, with versatile director James Mangold (“Ford v. Ferrari,” “The Wolverine”) taking the reins from that Spielberg fella, “Dial of Destiny” has afew clever ideas and some well-crafted action sequences, but the main plot line is creaky, corny and contrived, and the final action twist lands the story in such disastrous, B-movie territory that not even Harrison Ford as Indiana Jones can rescue it from collapsing in a dusty heap of mediocrity. (There’s a last-ditch effort to give Indy some closure, but it feels tacked-on and halfhearted.)

The story kicks off with an extended prologue set near the end of World War II, which means Indiana Jones would be in his mid40s, and I must say the de-aging technique used on Ford is maybe the most impressive use of the technology yet. Accompanied by his geeky pal Basil Shaw (a wellcast Toby Jones), Indy is trying to get his hands on a piece of the Antikythera, aka the Archimedes Dial, a frighteningly powerful contraption that is said to hold the powers to manipulate fissures in time. Whatever, it’s the thing everybody wants.

Indy finds himself in a deadly battle atop a train, against the backdrop of some pretty terrible CGI, with one Jürgen Voller, a mad Nazi scientist who is played by Mads Mikkelsen, and while Mikkelsen is a wonderful actor, it feels a bit lazy to cast him again as the heavy. Indy gains possession of the Antikythera. Another successful adventure for Indiana Jones!

Cut to 1969, about a dozen years after the events of “Crystal Skull,” and we find Indy living out his days as a crusty, surly old-timer who wakes up in his cruddy apartment in New York, pours bourbon into his coffee and heads to his job teaching at Hunter College, where he goes through the motions while boring his class to death.

Enter one Helena Shaw (Phoebe Waller-Bridge), the daughter of Indy’s old and dearly departed friend Basil, whom he hasn’t seen in more than a decade. Helena claims she’s writing her doctoral thesis on the Dial of Destiny gizmo, but in fact she’s a duplicitous, manipulative fortune-hunter who intends to steal Indy’s half of the thingee and auction it to the highest bidder.

Greatly complicating matters: the return of Jürgen Voller, who has reinvented himself as a scientist for NASA but will now stop at nothing to gain possession of both halves of the gizmo thingee, so he can travel back in time and alter the course of World War II. Great, we haven’t had a “travel back in time to alter events” plot in at least a couple of weeks.

Director Mangold stages an audacious-bordering-on-cartoonish chase sequence that careens through an Apollo 11 celebration parade and then a Vietnam War protest. The action then hops to a number of exotic locales, including Tangiers, Athens and Sicily, with one extended chase sequence after another, proving that a movie can be both action-packed and slowmoving at the same time.

Phoebe Waller-Bridge is a phenomenally talented actor and she does her best to infuse Helena with a kind of old-timey Katharine Hepburn energy, but she’s saddled with playing a one-dimensional character. Helena’s young partner in crime, the plucky and resourceful Teddy (Ethann Isidore), is an obvious attempt to echo Short Round, while Antonio Banderas shows up out of nowhere as an old buddy who apparently has just been waiting around with his crew to do a big favor for Indy.

Even when the stakes are enormous and the threats are real, Indiana seems more resigned to being forced into one last big adventure than excited and charged to be back in the game. Trust us, Indy; we know how you feel.

‘INDIANA JONES AND THE DIAL OF DESTINY’ ★★
Disney presents a film directed by James Mangold and written by Mangold, Jez Butterworth, John-Henry Butterworth and David Koepp.

Running time: 144 minutes. Rated PG-13 (for sequences of violence and action, language and smoking). Opens Thursday in local theaters.