The final chapter in Phase Two of the Marvel Cinematic Universe, "Ant-Man" stays pretty safely within the wheelhouse of what has gone before, choosing sturdy, if familiar, professionalism over creative daring. As directed by Peyton Reed (2008's "Yes Man") and written by Edgar Wright & Joe Cornish (2011's "The Adventures of Tintin") and Adam McKay (2013's "Anchorman 2: The Legend Continues") & Paul Rudd (2008's "Role Models"), the film is comparatively lighthearted next to the likes of 2014's "Captain America: The Winter Soldier" and 2015's "The Avengers: Age of Ultron," lending a quirky sense of humor to what is structurally an obligatory origin story. The premise of a superhero who shrinks to the size of an insect sounds silly—even wayward scientist Darren Cross (Corey Stoll) says as much early on—and yet Reed makes the minuscule physical size of his action sequences a part of the film's charm by giving his tiny lead character an uncommon perspective of the enormous world around him.

Professional cat burglar Scott Lang (Paul Rudd) has just served three years at San Quentin Penitentiary, but now he is out and hoping to turn his life around for young daughter Cassie (Abby Ryder Fortson). Desperate to find a job but having trouble doing so with a prison record, he begrudgingly lets excitable pal and fellow ex-con Luis (Michael Peña) talk him into what he claims is one last foolproof score. What he finds in the safe he is targeting, however, isn't money, but a peculiar suit with the powers to shrink and strengthen its wearer, long kept in hiding by brilliant physicist Dr. Hank Pym (Michael Douglas). Forty years ago, Hank cracked the code on what he called the Pym Particle, a subatomic formula that he vowed he would never allow get into the wrong hands. Now, Hank's former protégé, Darren, has taken over Pym Industries and is determined to replicate the code in order to militarize an ant-sized army. Much to the chagrin of headstrong daughter Hope van Dyne (Evangeline Lilly), Hank has chosen Scott for the important mission of overthrowing Darren's destructive plan and, in effect, saving the planet.

"Ant-Man" had a fair share of behind-the-scene difficulties, most notably the loss of original director Edgar Wright, who chose to step down prior to filming due to creative differences. While much of Wright's pre-production work was used—he still receives story and writing credits—Paul Rudd and Adam McKay were brought on soon after to contribute to the script. It is a testament to the finished product, one supposes, that any drama there may have been did not carry over to what has found its way to the screen. As is frequently the case with Marvel, there is the gnawing feeling while watching the movie that it could be better, braver, and more open to conceptual risk-taking. The jauntier tone is welcomely reminiscent of 2014's "Guardians of the Galaxy" (possibly the best of all the Phase One/Phase Two MCU entries, to date), but the narrative is routine and slightly labored, and the characters could use a little breathing room to grow beyond the constricting, all-business restraints of the plot.

The first hour and change diverts, to be sure, but it is mere set-up to a third act that finally takes off the way the entire film should have. For increasingly understandable reasons, 1989's "Honey, I Shrunk the Kids" is never far from mind, but what is surprising is Reed's Joe Dante-esque inspiration during the homestretch. Inventive and playfully twisted, the climax concocts some delicious set-pieces, from the shrunken Scott's race through a model cityscape blowing up around him to a high-stakes confrontation atop a Thomas the Tank Engine train set. Apple's voice assistant Siri, The Cure's "Plainsong," and an electric bug zapper also cleverly figure into the proceedings.

Paul Rudd has more than paid his dues with a steady, more-than-respectable career that has tended to typecast him as a perpetually affable personality in mid-range studio comedies. While his part of Scott Lang isn't that much of a stretch, his new role as an unlikely and courageous superhero most definitely is. Even when he's playing a petty criminal, it is impossible not to empathize with him as he more than anything wants to show ex-wife Maggie (Judy Greer) that he is responsible enough to once again be a part of their daughter's life. Michael Douglas (2010's "Wall Street: Money Never Sleeps") brings a dignified, albeit stubborn, dignity to Dr. Hank Pym, who is hoping to reclaim his relationship with his own daughter. Evangeline Lilly (2014's "The Hobbit: The Battle of the Five Armies") gives Hope a tough, spirited drive as she strives to prove to her dad that she is as capable as any of the men around her who are entrusted with more responsibility. As resident heavy Darren Cross, Corey Stoll (2014's "This Is Where I Leave You") is effectively snide, if given few chances to be anything other than rotten to the core. Meanwhile, Michael Peña (2012's "End of Watch"), as the energetic, fast-talking Luis, is contagiously entertaining playing a close cousin to his character in 2009's whip-smart, blackly hilarious satire "Observe and Report." Rounding out the cast are Judy Greer (2015's "Jurassic World"), a perpetual bright spot in any picture in which she appears as Scott's patient ex-wife Maggie; Bobby Cannavale (2014's "Annie"), revealing a shade or two more than initially expected as Maggie's new husband, police officer Paxton, and Abby Ryder Fortson (TV's "The Whispers"), adorable as little Cassie.

As the latest Marvel comic-book property to receive a big-budget film adaptation, "Ant-Man" roughly places in the middle of the pack, a fantastical heist adventure that rigidly adheres to the superhero-origin blueprint but at least does so with charisma to spare. Because so much of the film is decidedly standard from a narrative viewpoint, it is the interludes where it dares to put a spin on things that are most memorable. Scott's experiences being a speck of his normal human size are visually captivating and all the more intriguing because of his unique vantage point. Luis' storytelling, depicted in flashbacks where his voice amusingly dubs that of everyone in sight, is superbly realized, an undeniable ode to Comedy Central's "Drunk History." The film's mid-credits punctuation mark will not be disclosed, except to say that with just one line—"It's about damn time"—it makes a bold statement in response to criticisms that there has been a dearth of strong, prominent female characters in Marvel's oeuvre. This long-overdue feminist declaration notwithstanding, "Ant-Man" is not especially deep and its dramatic mark is slight at best. Taking itself seriously without being too serious, the film proves fun all the same, confirming that it is possible to side with a superhero who is the size of a fingertip without once feeling the need to laugh at him.