Ron Howard and Tom Hanks return to familiar—indeed, over-familiar—territory with their third adaptation of a Dan Brown globe-trotting conspiracy thriller. After “The Da Vinci Code” (2006) and “Angels & Demons” (2009)—filmed in reverse order from that of publication, presumably because it was “Code” that became such a huge success on the page—they’ve moved on to the fourth novel featuring Harvard professor of “symbology” and puzzle-solver Robert Langdon—published in 2013, skipping “The Lost Symbol” (2000), perhaps because they didn’t want to offend Freemasons, who provide many of its main characters. (Of course, they were never sheepish about possibly offending Catholics.)

In any event, the quasi-religious motifs are abandoned in “Inferno,” despite the plot’s being constructed to some extent around the first part of Dante’s “Divine Comedy.” Shedding them, however, has resulted in a plot that seems not less but more ridiculous. The premise is that Bertrand Zobrist (Ben Foster), a billionaire-cum-guru with a Malthusian streak, decides to confront what he sees as the threat of world overpopulation by unleashing a virus that will kill off half the world’s people within a couple of months. For some reason instead of just doing the deed himself like any respectable mad scientist, he’s arranged, along with a coterie of acolytes, for its release at a particular time and place. Even more inexplicably, he’s prepared an elaborate series of clues, all of them related to Dante, that will reveal the particulars of his scheme to anybody smart enough to figure them out. Of course, had he not done so there would be no plot—which might, in the eyes of many readers and moviegoers, have been a blessing.

In any event, the narrative kicks in with poor Langdon awakening in a hospital in Florence after Zobrist’s death (we see him fall—or rather jump—from a picturesque Florentine tower after being pursued through the streets by a trio of dangerous-looking guys dressed all in black, the most notable of whom is played by Omar Sy). Langdon is being ministered to by Dr. Sienna Brooks (Felicity Jones) after being brought in with a superficial bullet graze to the head that’s left him with partial amnesia. But there’s a trade-off of sorts: he might not be able to recall the word “coffee,” but he does have visions. Unfortunately, they’re horrible visions featuring lurid imagery from Dante’s “Inferno.” (They’re all pretty dreadful in terms of cinematic effects, too; no wonder that they’re shot so murkily and edited so chaotically.)

In any event, soon Langdon and Brooks are in flight from a murderous policewoman (Ana Ularu) who bursts into the hospital with her gun blazing. They will eventually follow Zobrist’s path of clues—which they conveniently stumble upon and all too easily decipher—from Florence to Venice and then Istanbul, which turns out to be the epicenter of the viral release. It would be a tedious business to go over the clues themselves—they include a dangerous-substance medical cylinder that turns up in Langdon’s pocket, Botticelli’s painting of Dante’s circular inferno, and Dante’s death mask itself, which turns out to have plenty of room on its reverse for an extremely long-winded message. What’s more important is that they will be pursued along the way by a couple of groups: the World Health Organization, with which Christoph Bouchard (Sy) and the professor’s one-time colleague (and perhaps future squeeze) Elizabeth Sinskey (Side Babett Knudsen) are associated, and a clandestine security outfit hired by Zobrist that’s headed by a mysterious fellow named Sims and called “The Provost” (Irrfan Khan). Rest assured that there will be plenty of purported surprises and double-crosses on the way to a clumsily choreographed and sloppily shot finale in which the world is—you guessed it—saved.

There’s one aspect in which “Inferno” is superior to its predecessors: it’s shorter. Unfortunately, at a “mere” two hours its relative brevity comes at the cost of coherence. A rushed tempo is combined with truly ugly hand-held cinematography by Salvatore Totino (which also casts a gloomy, bleached-out pallor over everything, although the locations themselves are quite beautiful) and editing by Dan Hanley and Tom Elkins that specializes in blurry montages of confused recollections and jerky flashbacks. The sound recording seems subpar, too—or maybe it’s just the cacophony of accents that makes some of the dialogue difficult to grasp.

Obviously this is not the finest hour for either Howard or screenwriter David Koepp. For the director, who’s had a string of disappointments, it seems to represent the old Hitchcockian tactic of “running for cover,” going back to the tried-and-true. You have to give Koepp credit for even attempting to wrestle Brown’s tome into some sort of respectability; he fails, but rarely abjectly (there’s an exception in the brief clip in which Zobrist enthuses about the Black Death bringing about the Renaissance—which seems a crude attempt to recall Orson Welles’ famous speech about Switzerland and Italy from “The Third Man”).

As for the acting, for the most part the cast treat the screenplay with an earnestness that’s literally deadly in this case. The only person who slyly sends up the material, practically winking at the audience to let them know that he’s well aware of how trashy the stuff is, is Khan. His performance might actually elicit an occasional smile of appreciation in a picture than otherwise deserves only derisive laughter.

“Inferno” is just another heaping helping of hopeless hokum from the team of Brown, Howard and Hanks—a scavenger hunt of historical nonsense and thriller clichés served up in an indigestible stew.

But you can’t complain, since it does advertise itself as hellish punishment.