Moonrise Kingdom isn't the only blue rumination on age and time opening in theaters this weekend. No, there's also Men in Black III, an ostensible sci-fi comedy caper that is actually a sighing contemplation of regret and the random bits of chance that shape our lives. Honestly! That is very much what Men in Black III, a surprisingly philosophically ambitious but ultimately anemic effort, is about. Perhaps only half on purpose, though.

When we see our old friends Agents J (Will Smith) and K (Tommy Lee Jones), for the first time in ten years, they're up to their usual stuff, cleaning up goopy alien oopsies and using their Neuralyzers to erase the memories of any civilians who might have witnessed the extraterrestrial fracas. K is the weary stern guy, J the youthful sass-mouth, just as we've always known them. Only, now when J wipes people's memories he doesn't plant life-bettering messages in their heads like he used to ("Hire an interior decorator to come here quick cause.....Damn."), he berates them about using cellphones on airplanes and lying to their kids. J has turned into a bit of a crank himself, and Smith now plays him with a bitterer edge. He's darker, more caustic. Part of this might have to do with an active character choice — J has been at this job for fourteen years, after all, so it makes sense that he'd be a bit sourer than when he was a plebe — but I also think this sharpness is a byproduct of Smith's own age and his working desperately to liven up Etan Cohen's curiously inert script. Smith earns a few genuine laughs here and there in the movie, but he also peddles like a madman (he's actually mad) through much of the material.

But yes, Smith seems harshed by age, and it's often unpleasant to watch. Then, as if to temper that by rebalancing the age gap, we are given a forty-years-younger Agent K. You see, a big bad murderer alien named Boris (Jemaine Clement) has escaped from moon prison (where are you when we need you, Guy Pearce?) and is hellbent on traveling back in time to settle a score with K and bring about the destruction of Earth. Though time travel has been made illegal, due to ripple effect dangers, there are one or two machines left in New York, which is where Boris is headed. There are a couple of action scenes in the present day, the biggest one a culturally iffy showdown at a Chinese food restaurant, but pretty soon we are headed back into the past. Once Boris goes back, the world changes and everyone seems to think that K died in the line of duty in 1969. Only J can remember him, or rather the alternate timeline him, so through the time warp he goes to rescue his pal and save the world. The time travel sequence is a woozy delight — J has to jump off the Chrysler building and activate the machine just before he hits the ground. When he does, time stretches and bends as he passes through various time periods, including the dinosaur era and the Great Depression. It's a clever bit that director Barry Sonnenfeld stages with panache.

Once J has arrived in Mad Men's Manhattan (I'll admit to strangely hoping for some sort of Don Draper cameo), he heads straight after Boris, hoping to get the job done quickly and eager to avoid interacting with K. Supposedly such a meeting would cause some unpleasantnesses that are never really elucidated, but one would guess that J futzing with K in the past would have some effects on the future, etc. The time travel paradoxes are never quite satisfied in this movie, though to be fair they rarely are in any time tripping tail. Of course, this being a buddy movie, J is unable to avoid K, who is now played by Josh Brolin, doing an uncanny and admirable Tommy Lee Jones impression. The vocal tics and curt manner are perfectly on pitch, as is that hushed, barely perceptible sentimentality that TLJ always has hiding somewhere in those crinkly eyes of his. J quickly convinces K that he is a time traveler from the future and they set off in pursuit of Boris, a trip that will take them to a party at Andy Warhol's Factory (an inspired bit featuring a funny turn by Bill Hader as Warhol), to an empty but haunted Shea stadium ('69 was a big year for the Mets, after all), and down to Cape Canaveral just in time for the launch of Apollo 11. The movie bounces along through all of this nicely enough, except it keeps picking up brown flecks of sadness as it goes, eventually turning the whole thing into a wistful contemplation of, well, temporal existence.

See, along the way J and K meet a friendly alien named Griffin (Michael Stuhlbarg, as warm here as he is cold on Boardwalk Empire, though just as calm and saturnine), a "fifth-dimensional being" who is capable of seeing all potential outcomes of all things, all at once. So he can read the future but not linearly, it's a broad field of possibility. He of course uses this blessing/curse to help the agents on their quest, but he also pauses, and the film pauses with him, to shed thoughtful light on the mysterious tricks of fate that make up any human life, the what ifs and unexpected turns, the small bits of chaos theory that make our lives both impossibly random and strangely fixed. We are at the whims of a whirring, interconnected universe and so we probably shouldn't regret things, or even fear death. We should ride time's wind like sailboats. Yeah, the movie kinda goes there.

Well, OK, that's maybe a big "kinda." It hints at it. It dabbles its toe in. But even a dabble is surprising for a movie of this kind. Sure the previous two Men in Blacks had their moments of sentimentality — K trying to retire, J losing his love to space — but this here is a little different. There's a reveal at the end that tightens J and K's bond in a distinctly dramatic way, there are whiffs of melancholic star-crossed thwarted romance, there's a monologue about baseball players that verges on poetic. In this regard, Men in Black III is a thoroughly surprising movie.

Unfortunately most everything else feels rote. The central conflict doesn't generate much heat, there's an urgency that's somehow missing, and certain narrative threads wind up at dead ends. (That romance, for example.) Jones is only in the film's present-day bookends, but even with half the workload he seems uninterested; if not bored, definitely tired. Smith, too, is out of step, relying too heavily on his own faded Q score. The best performances are from the newbies, with Brolin charmingly rising to the gimmicky assignment before him and Stuhlbarg walking in from a different movie and walking off with this one.

Men in Black III is a curious item, a nostalgia trip inside a nostalgia trip. An alien comedy about the ruefully funny absurdities and mysteries of regular human life. It doesn't exactly work, but you have to wearily appreciate the effort.