Spoiler alert!

If I had to select one image to sum up the Marvel Cinematic Universe, I might go with the recurrent, claustrophobic close-ups of billionaire inventor Tony Stark (Robert Downey Jr) frowning inside his Iron Man helmet, in the thick of the action yet removed from it all.

Tony at these moments looks as if he were straining to hold the entire world in his head, which is how the brothers Anthony and Joe Russo must have felt as the directors of Avengers: Endgame, the all-star three-hour culmination of the run of Marvel movies that began with Iron Man in 2008.

Respect is due to the Russos and their many collaborators for bringing off this near-impossible engineering feat. Given all the characters and storylines that have to be serviced, the movie is lighter and more shapely than it has any right to be, with the pacing problems that plagued Joss Whedon's similarly epic Avengers: Age of Ultron largely resolved.

It helps that the thrust of the story remains straightforward. We pick up where last year's Avengers: Infinity War left off, with the villainous Thanos (Josh Brolin) having succeeded in his long-term goal of wiping out half the population of the universe.

Among those still standing are the six original AvengersTony, the Hulk (Mark Ruffalo), Thor (Chris Hemsworth), Captain America (Chris Evans), Black Widow (Scarlett Johansson) and eternal afterthought Hawkeye (Jeremy Renner).

The task of reversing this catastrophe falls to them, with help from a few ring-ins, among them the grouchy Rocket Raccoon (voiced by Bradley Cooper)his temper not improved by the loss of his fellow Guardians of the Galaxyand the buoyant Ant-Man (Paul Rudd), initially presumed dead but in fact merely trapped within the "quantum realm". Delightfully, it's Ant-Man who does the most to dispel the morose mood of the film's first half-hour, proposing a hare-brained scheme that involves a literal return to the past.

By this point, the plot has leapt forward five years, allowing the heroes to adjust to the new normal. Tony, supreme narcissist that he is, has settled down with true love Pepper Potts (Gwyneth Paltrow) and become the doting dad we can see in retrospect he was always meant to be. The Hulk has found a way to fuse the brainy and brawny sides of his nature, gaining in maturity what he's lost in raw power.

Thor has gone through the funniest metamorphosis of all, which I won't try to describeexcept to say it's gratifying that Hemsworth, who began as a rather one-note character, now ranks with the most valuable comic players of the saga.

The leading exponents of the Marvel house style, the Russos remain team players rather than visionaries: what we're offered here is a kind of glorified TV finale, part soap opera and part sitcom, premised on cross-cutting between storylines and on the understanding that acting is the most fundamental of special effects.

The idea is that these nonsense plots have to be juiced up with real emotions, even as correct proportions of bombast and bathos are fed into every scene. It's of the essence that we're shown Captain America attending a support group and Iron Man doing the washing up.

A major thematic concern is parents and children, and how legacies are or aren't passed on: Thanos is the ultimate Bad Dad, while Tony has finally taught himself to be a good one. Simultaneously, the time travel premise enables the series to reflect on and critique its own past, acknowledging that the premise of a superhero team dominated by white guys (and, OK, one green guy) would hardly fly if it were launched today.

Not even the most naive fan would take the title of Endgame literally. But the movie is designed, nonetheless, to mark the end of a cycleincorporating a series of farewells and handovers, and acknowledging that while some losses can be repaired, others cannot.

For young adults who have literally grown up with these movies, the experience may be emotionally overwhelming. The hint that we are all surrogate members of the Marvel family can also be seen as an uncommonly slick sales pitchbut right before the end credits I confess I too may have teared up, just for a moment.

Avengers: Endgame is released in cinemas on April 24.

-SMH/The Age