The third installment in the slow-moving “Mission: Impossible” movie series, which started up a full decade ago, makes a fundamental mistake: it tries to humanize the figure of Ethan Hunt by putting his lover into deadly danger at the hands of a horrible villain out for revenge against the hero. Good old Jim Phelps, the leader of the M:I team played by unflappable Peter Graves in the now-creaky television series, never bothered with a personal life (or at least was never shown doing so), and that’s the way viewers liked it. And burdening his modern counterpart with a subplot that detracts from the pure adrenalin-stoked action of the franchise was a bad decision from a purely narrative perspective–do we really want to see this sort of soap-operatic domesticity in an “M:I” movie?

But the choice is a particularly poor one because it’s Tom Cruise who plays Hunt. Perhaps there was a time when one could take this actor seriously in a role that required him to evince real emotion, but if so it’s long past. Cruise’s almost preternatural steely-eyed intensity both on and off the screen of late, whatever the antics, has turned him into a curiously robotic figure–he looks brainwashed, to tell you the truth (any religious allusion is purely accidental, of course)–and no degree of comic-book histrionics can succeed in effacing that image. In his hands Ethan Hunt remains an automaton, and the effort to invest him with feeling falls flat. It’s like watching a machine trying to look human. Indeed, at one point in the narrative–shown twice actually, once in flashback–Ethan sheds a tear, and you may well wonder whether a special effect was needed to get the shot. It also seems oddly appropriate that at one point in the narrative one of the characters–I won’t say which–actually comes back to life. Don’t androids often resurrect?

But aside from all that, the plot of “M:I 3” is–despite all the running and jumping, swinging and shooting, explosions and fights–so pedestrian that you may find yourself nodding off if you can tune out the noisy soundtrack. Basically, the script is a very simple one about the effort to derail Owen Davian (Philip Seymour Hoffman), an international arms dealer, from acquiring some sort of doomsday device (the MacGuffin, never explained and always referred to as the “rabbit’s foot”), and selling it to some unholy purchaser. Of course, that’s just the thread on which to hang a string of big action set-pieces. First up is a huge rescue operation in which a semi-retired Hunt is brought back into service by his boss Musgrave (Billy Crudup) to rescue Lindsey Farris (Keri Russell), an agent he’d trained who’s been captured by Davian; his new team consists of Luther (Ving Rhames), Zhen (Maggie Q) and Declan (Jonathan Rhys Meyers), and the mission closes with a dog-fight between helicopters in a field of wind turbines and Lindsey’s unfortunate end. Next comes a snatch job in which the team kidnaps Davian from a charity bash within the walls of the Vatican, no less (and “The Da Vinci Code” is still weeks away). A massive escape episode follows, which in turn leads to the snatching of Ethan’s new wife Julia (Michelle Monaghan) to force him to steal the rabbit’s foot from a Shanghai skyscraper to exchange for Julia. That theft, involving swinging between buildings and a long drop to the street, comes next, followed by the obligatory torture scene and a final confrontation, with happy fadeout of course.

Amidst all this, of course, the love between Ethan and Michelle is supposed to act as the emotional glue that holds everything together. But it’s never sufficient to paper over the plot holes and repetitions from previous installments. It’s never made clear what the “rabbit’s foot” is–all that we see is a cannister marked “biohazard” looking rather like one of those tubes one uses at a drive-in bank; that’s not a problem (in fact, it’s the function of a MacGuffin), but the fact that Hunt has to retrieve it for Davian raises a narrative difficulty: if Davian was getting paid for it at that Vatican meeting (what else could have been in the briefcase he takes?), how did he intend to get it had not Hunt happened along? Or am I missing something? Could it be connected with the fact that there’s a traitor within the American intelligence network manipulating everything? I won’t reveal his identity, which is supposed to be the movie’s big closing revelation (though almost everybody will guess it well in advance), but I fail to see how that person could have arranged things; and in any event I must point out that it’s a twist borrowed from the first installment of the series (anyone remember Jon Voight?) Then there’s the mask business. The kidnapping of Davian involves Cruise becoming his double. This is an old “M:I” trick, of course, but it was always outlandish back when Martin Landau did it, and it was even worse in “M:I 2,”where it was taken to ridiculous extremes. And it’s no better here. The overuse of the trope in which Hunt falls from a great height, only to be stopped just before hitting the surface by his bungee cord, is also repeated this time around–twice, in fact (unless I missed a third jump).

One could continue this catalogue indefinitely, but enough’s enough. Plausibility is not this movie’s strong suit; and neither is invention. On the other hand, you have to admit that though the action bits may be familiar, they’re certainly well pulled off by Cruise, director J.J. Abrams and what must have been a small army of stunt men and special-effects wizards. Abrams doesn’t show the visual flair of either Brian De Palma or John Woo, who presided over the first two installments, but he keeps things moving along and, with able support from ace cinematographer Dan Mindel and editors Mary Jo Markey and Maryann Brandon, makes the various episodes swift and seamless. The secondary human performers don’t fare as well. Monaghan is mostly bland and timid until she gets to be the action heroine at the close, and of Hunt’s team, Rhames makes an impression by reason of his presence and a few good lines, but Rhys Meyers and Maggie Q are pretty much relegated to the sidelines; and while Laurence Fishburne exudes officiousness as the intelligence chief, Crudup comes off pallid as Hunt’s boss. But the biggest disappointment has to be Hoffman, not because he doesn’t bring an air of nastiness and authority to the role, but because his part is so thinly written. One would expect the script would have given an actor of his caliber a bit more to do than simply act like a second-rate James Bond villain, but Davian isn’t really much more than that. A pity. The rest of the cast are about as disposable as the bullets used to off so many of them.

As a summer time-waster that provides an empty adrenaline rush, “M:I 3” will do. But it doesn’t represent an advance on the first installments, and it does go on. And in the final analysis it doesn’t accomplish what seems to be the real impossible mission: getting Tom Cruise to act like a genuine human being.