When writing about The Avengers, there's a temptation to get hung up on logistics. Half a decade in the making and resting on a foundation laid by no fewer than five movies (Iron Man, 2008; The Incredible Hulk, 2008; Iron Man 2, 2010; Thor, 2011; Captain America: The First Avenger, 2011), the pinnacle of Marvel's ongoing effort to convert several decades' worth of comics continuity into blockbusting, movie-sized chunks combines the four main characters of those movies as well as many of their hangers-on and supporting cast, and aims to tell the story of how they formed the eponymous superhero team. For a single film to pay sufficient attention to four characters who had previously headlined their own stories (as well as the stars portraying them), and establish several new superheroes, and bring them all together in a compelling fashion, and tell an engaging story besides, feels less like artistry and more like a feat of engineering. One feels obliged to be impressed that the thing was done at all, whether or not it was done well.

Which is not to say that The Avengers is badly done. It checks most of the items on the list above in a largely entertaining fashion, and achieves, as a whole, that gold standard of Marvel movies—it is a lot of fun. But The Avengers comes to us written and directed by Joss Whedon (with an additional story credit for Zack Penn), who in 2005 brought us Serenity, one of the most nimble science fiction action-adventure films in recent memory, and a film that, like The Avengers, had a large and varied cast each vying for their moment in the sun, a complicated setting, and wealth of backstory to address. True, Whedon would in some ways have had an easier time of it with Serenity—he was working with his own characters and world, continuing a story he had overseen himself in the television series Firefly (2002-2003), and working, presumably, without the executive interference for which the Marvel film franchise has become famous. Nevertheless, it's hard not to draw unflattering comparisons between the two films' opening acts, which introduce the characters, the setting, and the challenge (and villain) that our heroes will be squaring against.

In Serenity, all this is achieved in a svelte and engaging fifteen minutes or so, which transition from dream to recording to reality and from one end of the solar system to another, and leave us, at their end, not only caught up with the story but caught up in it. The Avengers takes longer to do less, and its plodding first hour is, in what feels almost like meta-commentary, mostly taken up with logistics. We learn a lot about how S.H.I.E.L.D.—the organization that has lurked in the background of the previous Marvel movies—works, and meet some of its key players—director Nick Fury, agent Phil Coulson (Samuel L. Jackson and Clark Gregg, reprising their roles from the previous films), and agent Maria Hill (Cobie Smulders, new to The Avengers and surprisingly underutilized for how prominently she's featured in its early scenes). We're taken to an enormous, teeming S.H.I.E.L.D. facility, which is quickly reduced to rubble when one of its top secret projects—the Tesseract cube which also acted as the McGuffin of Captain America—disgorges Loki (Tom Hiddleston), brother of Thor (Chris Hemsworth) and villain of Thor, who makes snide threats, steals the cube, and brainwashes several characters into helping him destroy humanity.

There follows a rather dispiriting sequence of essentially identical scenes in which the team is cobbled together. Some of these are entertaining—the scene in which Tony Stark (Robert Downey Jr., who achieves the nifty trick of turning down the wattage on his performance just enough to let the film's other main characters come to the fore without compromising his character's narcissistic need to always be the center of attention) is forestalled in his plans for a romantic evening with Pepper Potts (an adorably bubbly Gwyneth Paltrow) by the arrival of Coulson is a welcome reprise of the three characters' rapport from the two Iron Man movies, all crackerjack dialogue and the welcome puncturing of Tony's ego by Pepper's acid-tinged indulgence and Coulson's deadpan determination. But soon the sameyness of these introductions—a S.H.I.E.L.D. agent interrupts the characters as they go about their lives, they initially refuse to join the fight against Loki, then agree once the stakes are made clear—becomes wearying, so that by the time that Thor makes his relatively idiosyncratic appearance, breaking through the barriers between his reality and ours in order to work out his issues with Loki and ending up in a knock-down fight with Iron Man in which Captain America tries and fails to play peacemaker, it's hard to enjoy, so ready are we for the preliminaries to be over and the story proper to begin.

Once the preliminaries are over, however, The Avengers kicks into gear in a big way—though not, it must be said, in terms of plot, which never rises above the vagueness of both the Tesseract cube as a McGuffin and the stock villains, aliens called the Chitauri, whom Loki plans to unleash on Earth using its power. This is very much in keeping with the previous Marvel films, whose plots were flimsy affairs aimed primarily at showcasing their heroes' outsized personalities—Tony Stark's narcissism, Steve Rogers's quiet nobility, Thor's good-humored bluster. Once The Avengers forces its characters together aboard S.H.I.E.L.D.'s flying aircraft carrier, the energy given off by the clash of those personalities is enough to power the rest of the film, flimsy plot or no. It's for this reason—and not simply because he's one less character for Whedon to introduce—that Loki is such a good choice for the film's villain. The best of a rather unimpressive roster of poorly motivated, indifferently characterized Marvel movie villains, Loki not only nearly walked away with Thor but consistently elevated its one-dimensional title character by playing up the mingled love and hate that lie between the two brothers. Thor's muddled third act did away with most of the character's complexity, so he is a less engaging figure in The Avengers, but he does manage to engage with almost every one of the film's heroes. Rather than fight against the essential paltriness of Marvel movie villains, Whedon plays Loki's up—no matter how great a threat he poses, there is never any doubt in our or the characters' minds that Loki is a loser, someone whose fundamentally pathetic nature shines through even their greatest achievements as a constant reminder that these are only temporary. The contempt this breeds in the other characters leads them to let down their guard, leaving them vulnerable to the barbed wit and keen insight that are Loki's only true weapons. (The one character who does not benefit from Loki's presence is Thor, who after angsting for a while about their troubled sibling relations fades into the film's background. Absent the fish out of water humor that was Thor's saving grace, there doesn't seem to be much life in the character.)

What's perhaps most interesting, however, about Whedon's choices in The Avengers is how relatively little attention he pays to his ensemble's big guns, Tony Stark and Steve Rogers (Chris Evans). There's obviously a lot of mileage to be gotten out of the conflict between Tony's self-absorbed cynicism and Steve's selfless idealism, and Steve has an affecting story of his own, having slept through the last seventy years and lost much of his sense of purpose since his awakening. The Avengers does gesture towards both of these stories (and in interviews Whedon has revealed that the latter, at least, was shot and then cut from the film's final version) in a way that is quite satisfying, but the bulk of its energies are spent building up the new or previously underserved members of the team, most notably the Hulk. Though technically not a new character, the Hulk is probably the most beleaguered figure in the Marvel movie franchise, haunted both by Ang Lee's infamous 2003 film treatment Hulk—still a byword for how not to do comic book movies—and its tepidly received 2008 reboot The Incredible Hulk (itself overshadowed by the success of Iron Man that same year). The star of the latter film, Edward Norton, has been replaced in The Avengers by Mark Ruffalo, which initially seems to herald yet another failed attempt to crack the character, and instead augurs the character's arrival. Where The Incredible Hulk's Bruce Banner was earnest and uncomplicatedly heroic, The Avengers's version is a more cynical, weary figure. Ruffalo's rumpled appearance, his muttered speech and downcast eyes, initially suggest a mild-mannered, bumbling Banner, but he soon reveals a sharp mind, a sardonic wit, and most importantly, a profound bitterness, both at his misfortune and at the way that bodies as diverse as S.H.I.E.L.D. and Loki seek to take advantage of it. Far from a stark Jekyll and Hyde division, Ruffalo and Whedon's Banner has the Hulk constantly bubbling under his surface, and the other characters' mingled sympathy and wariness of him feel entirely earned—as does Banner's revelation, at the end of film, of how he (mostly) manages to keep the Hulk in check.

Another character who gets the chance to shine in The Avengers is Scarlett Johansson's Natasha Romanov, a former assassin known as Black Widow. Johansson had a small and thankless role in Iron Man 2 that, like the previous Hulk movies, did not inspire optimism for her presence in The Avengers, but once again Whedon serves the character well. On paper its least imposing member, and a long-time S.H.I.E.L.D. operative who, in both Iron Man 2 and The Avengers, is dispatched to retrieve and recruit some of its other members, Natasha is an outsider to the team, dubious about the ability of these fractious personalities to work together and only grudgingly trusted. Whedon, however, makes the choice to tell much of the story from her point of view, as an observer of the team's early interactions and its individual members, and of the growing crisis sparked by Loki. She is thus both an audience surrogate and the person whose actions have the most effect on the plot—it's Natasha who convinces the reluctant Banner to come aboard, and she who is able to prise Loki's plans from him. She's also an intriguing character in her own right, whose storied personal history is hinted at but only partially revealed over the course of the film (a Black Widow movie is now being mooted), and who reveals an impressive array of skills as she squares off against Loki and her would-be teammates, more than holding her own against both despite having no actual superpowers. Somewhat less well-served is Hawkeye, who made an intriguing cameo in Thor (and is anyway played by the always excellent Jeremy Renner with his typical down to earth charm), but spends most of The Avengers in an altered state that leaves us very little chance to get to know him better. That's somewhat counteracted by the glimpses we get of his and Natasha's friendship, which gives both characters—and the organization to which they belong—a weight of history.

Even as it draws its characters more tightly together, The Avengers remains largely indifferent to its story. The team's unwillingness to embrace their role as heroes, long past the point where the risk that Loki poses to the Earth has been made clear, makes no sense, and the means by which they are finally persuaded to work together are mawkish and heavy-handed. At its heart, The Avengers is solid—it knows, and loves, its characters, and is never less than entirely generous in giving them and their relationships the space they need. And once the team does come together and the busywork of figuring out Loki's dastardly scheme has been done, the film's culminating action sequence—a battle royale in the streets of New York between the Avengers and the Chitauri hordes—is something to behold. A long, engrossing, multithreaded fight, it showcases the film at its best—fun, witty, and giving each of its characters, on and off the Avengers team, the chance to shine and play an integral part in saving the day. It's almost enough to make one forget the long and bumpy road we took to get to this point—almost, but not quite. One expects a bit more from a writer like Whedon—and perhaps also from a film as universally well received and commercially successful as The Avengers has been—than the same slapdash attitude towards plotting and pacing that has characterized Marvel's films over the last half-decade. That quality was excusable—or at least excused—by the knowledge that these films were less stories in their own right than stepping stones to something greater, a grand story that would bring these characters together in a way that would justify the flaws that came before it. Well, the characters are together, but the grand story has yet to materialize, and probably never will. There's a strong heart beating at the core of The Avengers, but the construction around it leaves much to be desired.

Abigail Nussbaum (anusbaum@netvision.net.il) is the Strange Horizons reviews editor. Her work has also appeared in The Internet Review of Science Fiction, Vector, Foundation, and the Israeli SFF quarterly The Tenth Dimension. She blogs on matters genre and otherwise at Asking the Wrong Questions.