Writer/director Joss Whedon's 2012 The Avengers wasn't the first film in what has become a cinematic juggernaut called the Marvel Universe, but it set a very high bar for the movies that followed. The Avengers was smart and funny and sacrificed none of the quirky individualism for which Whedon is celebrated; it's also the third highest-grossing movie of all time and Disney's biggest box office smash. The secret to the film's success was the way Whedon's screenplay integrated essential traits and backstories of all six Avengers into both the action and the banter during the film's first hour, making the story sensible even to those unfamiliar with the sprawling Marvel Universe. That is no small achievement.
But a lot has happened in the Marvel Universe since that time, including seven more feature films focusing on individual superheroes counted among the Avengers. That may be one reason why Avengers: Age of Ultron struggles for the delicate balance of the earlier film and appears overstuffed with characters, plot points and repartee that mostly seems forced. There's no question the visual effects and action sequences are state-of-the-art, and those seeking a roller-coaster ride at the movies will scarcely find disappointment. But The Avengers' seemingly effortless charm is nowhere in sight.
Age of Ultron's story doesn't really add up, especially if you make the mistake of thinking about it too much. Iron Man Tony Stark (Robert Downey Jr.) finds sophisticated artificial intelligence inside the scepter that belonged to the evil aliens in The Avengers and somehow blends it with his own innovations to accidentally unleash a foul-tempered and mentally unbalanced robot named Ultron (James Spader). How exactly did Ultron come into being and why does he hate people so much? How does artificial intelligence switch between robot forms like a ghost? There's not enough sense underlying this primary source of conflict, and that is where the film's problems begin.
The focus of the story shifts repeatedly, from an unconvincing romance between two Avengers to the mind control powers of Ultron ally Wanda Maximoff (Elizabeth Olsen) to the all-powerful Infinity Stones, which are a thing in the Marvel Universe but mean little in the context of this film. Whatever works to move things along at any given moment seems to get the green light. The story goes off the rails early, as if to signal that we should strap ourselves in for the ride and not worry too much about the details.
The constantly shifting perspectives of the Avengers movies' action sequences have become a signature style for Whedon, and this can be wonderfully transporting (and disorienting), as in Ultron's opening battle scene. The charisma of Avengers' lead actors is impossible to miss, and the use of unusual locations for a movie of this type — including Seoul, South Korea and Johannesburg, South Africa — makes for some fresh visuals.
It's unclear which actors will return for the next two Avengers movies (currently scheduled for 2018 and 2019) but it seems like the band is breaking up for good. Ultron's final scenes are devoted to the official introduction of a new generation of Avengers, who seem like they'll have a tough time maintaining the broad appeal of their predecessors. But the juggernaut continues.