Grade: B-

Like his previous picture “Spy,” Paul Feig’s “A Simple Favor” is about a woman’s transformation, but while the Melinda McCarthy movie was upbeat and slapstick-funny, this one is darkly humorous and kind of nasty. That doesn’t mean it’s necessarily worse, just very different—though it is, in fact, not quite in the earlier picture’s league.

Based on a novel by Darcey Bell, the plot is about the curious friendship that develops between Stephanie Smothers (Anna Kendrick) and Emily Nelson (Blake Lively). Smothers is a widow, but an incessantly chipper mother to her little son Miles (Joshua Satine); she also hosts a video blog in which she dispenses advice to moms about food, creative household projects and ways to keep the children happy, and is such a volunteer at school that organizers have to ask her to slow down and the neighbors joke about her endless effervescence.

By contrast Emily is a sharp-tongued, impeccably stylish career woman—she works in what passes for haute couture, keeping the house designers in line. She’s married to handsome Sean Townsend (Henry Golding), a novelist and English lit professor at a local Connecticut university, and they have a son, Nicky (Ian Ho), who’s a classmate of Miles’. As a mother she might be termed laissez-faire, but she and Stephanie strike up an odd companionship as their kids become best friends, and before long Stephanie is happily picking Nicky up from school when Emily is busy, or arranging elaborate playdates for the tykes. The two women also share the cold martinis Emily favors while talking about themselves—during which Stephanie reveals some pretty unsettling details about the deaths of her husband (Eric Johnson) and her half-brother (Dustin Milligan) in a horrific car crash.

The first part of the movie, with fluttery Stephanie and acerbic Emily playing off one another, is good, snarky fun, but then the plot kicks in. Emily asks Stephanie to pick up Nicky one day, and hours pass without word from her—hours that stretch into days. Sean is in London tending to his sick mother, and rushes back; as Emily’s absence grows longer, Stephanie becomes his helpmate, sending tongues in their Connecticut burg wagging. The police, led by a savvy, jocular detective (Bashir Salahuddin), begin to suspect something nefarious.

Most importantly, Stephanie decides to investigate on her own, using her vlog to solicit not just sympathy for the grieving husband but information on Emily’s whereabouts. It turns out that the missing woman’s actions were in fact curious. It also becomes clear that her marriage with Sean was hardly as perfect as it seemed to Stephanie on the surface. Suggestions of infidelity and reports of large insurance policies are added to the mix. Finally Emily is found.

But the mystery doesn’t end there, which is where “A Simple Favor” threatens to veer off the rails into nutty-noir territory. Stephanie looks into Emily’s past and uncovers some very dark secrets. These, quite frankly, show that the screenplay is more interested in brash deviousness than even the remotest touch of plausibility, and in the process of explaining things it relies on one of the hoariest, most clichéd revelations of the genre. But the main emphasis is on how, in the process, Stephanie becomes quite a different woman—though one you might not find all that attractive.

And, of course, it’s the very ludicrousness of the explanation that’s meant to provide fizz, and it must be said that Feig and his cast bring enough catty malevolence to the final stages to keep “A Simple Favor” from becoming a drag. After all, noirs were never known for their subtlety or logic, and in that respect this is true to their spirit while adding sleek modern touches, like John Schwartzman’s vivid widescreen color images, which take advantage of the locations, Jefferson Sage’s luscious production design and Renee Ehrlich Kalfus’ witty costumes without looking for an instant like the shadow-infected black-and-white style of the old classics even as the script drops blatant references to many of them, sometimes by title.

The cast certainly throw themselves into that spirit, with Kendrick reprising her agreeably nerdy shtick and even dialing it up a notch, and Lively offering a hilariously shrewish performance that can turn mean on a dime as needed. Golding makes a convincingly befuddled hunk, and nifty, scene-stealing supporting moments come from Andrew Rannells, Kelly McCormack and Aparna Nancheria as a gaggle of neighbors who serve as a sort of Greek chorus; Salahuddin as that Columbo-like policeman; and Rupert Friend, as an arrogant designer Stephanie takes down a peg.

“A Simple Favor” is hardly the equal of the Coens’ neo-noir films, but thanks to savvy direction and very capable stars it brings sufficient smarts to the party to remain enjoyable even through a goofy final act. If you found pictures like Harold Becker’s “Malice” or Robert Zemeckis’ “What Lies Beneath” (2000) to your liking, this movie will provide a similar cup of bitter tea.

Grade: B-

Though most Marvel superhero movies deal with threats to the whole planet, if not the entire universe, they’re all really about nothing more than providing juvenile thrills on a bloated scale. The initial Ant-Man movie, by contrast, didn’t claim to be concerned with anything but a fairly small crisis, befitting the petite size of the costumed protagonist, and while it didn’t eschew excitement, it was more about laughs.

The follow-up, which adds a superheroine to the mix, remains largely localized and comic as well. But being a sequel, it’s also bigger, with more extended action sequences and elaborate special effects. That’s not necessarily a good thing; in this case, however, it’s not fatal: “Ant-Man and the Wasp” is amusing enough to squeak by, though it’s overly busy and frantic, and the occasional attempts to fold it into the larger Marvel Universe (as in one of the end credit inserts) weigh it down.

As the movie opens, Scott Lang (Paul Rudd), the ex-thief recruited to be the new Ant-Man by the old one, genius inventor Hank Pym (Michael Douglas), is finishing up his house arrest for his role as part of the Captain America faction of the “Civil War” fracas; he’s trying to keep up a close relationship with his darling daughter Cassie (Abby Ryder Forstan), who’s living with his supportive ex-wife Maggie (Judy Greer, wasted) and her new husband Paxton (Bobby Cannavale, ditto). Meanwhile goofy FBI agent Jimmy Woo (Randall Park, pressing his dopey shtick too far) tries to catch Scott in any infraction that could extend the sentence.

But Lang is drawn into helping Pym, still angry with him for misusing the Ant-Man suit, and his daughter Hope van Dyne (Evangeline Lilly), now outfitted as The Wasp, in their effort to extract Hank’s ex-wife Janet (Michelle Pfeiffer), the original Wasp, from the Quantum Realm, the miniscule nano-world where she was trapped thirty years earlier, having shrunk to infinitesimal size to stop a runaway nuclear missile. Much of the humor lies in Scott’s having to get back home, where a giant ant has been assigned to wear his ankle bracket, in time to foil the FBI’s repeated attempts to catch him violating the terms of his sentence while helping Hank and Hope.

The frenzied action that follows juxtaposes the trio’s effort to rescue Janet with plot threads involving other characters. One focuses on Scott’s goofy partners in a would-be security agency—Luis (Michael Peña), Dave (Tip “T.I.” Harris), and Kurt (David Dastmalchian). In another, Ava, aka The Ghost (Hannah John-Kamen), a desperate young woman whom an accident conducted by her father, a former colleague of Pym, doomed to a precarious existence of phasing in and out of physical space, is determined to access Pym’s lab in order to cure herself; that strand also implicates another old colleague of Pym, an academic named Bill Foster (Laurence Fishburne). Then there’s nasty Sonny Burch (Walton Goggins), a trafficker in high-tech equipment, who also wants to get his hands on Pym’s lab.

That lab provides one of the movie’s cutest effects: not the interior, which is pretty generic despite a long tube that will lead to the Quantum Realm, but the exterior—the whole building can be miniaturized and carried off like a boxy suitcase. (The gag is overused, being applied also to cars and vans, but it’s still a good one.)

Other genuinely funny bits also involve transformations of a sort. In one case, Pfeiffer’s character takes over Rudd’s body from the quantum world to correct a mathematical formula, and Rudd’s impersonation of her clipped delivery is a gem. Then there’s the episode in which Luis, under the influence of a “truth serum” (itself the subject of some funny dialogue), recites a long account of past events, accompanied by a montage of flashbacks in which the people he’s talking about lip-synch to his voice. Peña’s rapid-fire delivery sells the bit, even though it’s a repeat of one from the first movie.

Much of the humor in “Ant-Man and the Wasp,” though, is pretty juvenile, with the FBI stuff particularly flat, though most of the material with Goggins, doing his usual sleazy routine, is also awfully thin. Rudd gets off a few good quips, like one in which he ridicules the scientific mumbo-jumbo by asking whether they’re just putting “quantum” in front of everything (perhaps he wrote the line himself), but a lot of the dialogue is no great shakes.

The effects are similarly hit-and-miss. The best one in the first movie was making Michael Douglas look young in the flashbacks. That’s still the case here, and it’s applied briefly to Pfeiffer as well (the younger Fishburne, on the other hand, is played by his son Langston). By contrast the rest of the VFX is solid enough (the exception being when Ant-Man switches to giant mode near the close), but—apart from the in-and-out-of-phasing of Ghost, whom Kamen plays with a degree of intensity that seems suited to a different, more serious movie—unremarkable. Still, the relative cheesiness feels of a piece with the whole movie, which lacks the titanic grandiosity and self-important tone of most Marvel product.

Otherwise the technical aspects of the movie are fine, with Dante Spinotti’s cinematography and the editing by Dan Liebental and Craig Wood doing a reasonably good job of coping with the jumpy narrative and splashy effects.

Though in every respect a lightweight addition to the Marvel canon, the innocuous “Ant-Man and the Wasp” is mildly enjoyable. By the way, if it’s Ant-Man, shouldn’t it be Wasp-Woman? Just asking.