Fair warning: considerable spoilers follow – read after watching.

Hey, no, seriously, don’t even think of reading this before you watch it.

People are going to talk about that ending for a whole year.

This is my main takeaway after watching Avengers: Infinity War. It may be the most visually stunning film in the Marvel Cinematic Universe, it may be packed with fantastic character moments and performances, and it may have set the standard for action scenes in superhero movies for years to come. But people are going to talk about that ending for a whole year.

We pick up the action immediately after the post-credits scene from Thor: Ragnarok, with the Asgardian refugee ship under attack from Thanos and the Black Order, his quartet of extra-terrestrial thugs; the big purple villain is on a mission to collect all six of the infinity stones so that he can wipe out half the population of the universe. Thanos despatches the Asgardians – including fan favourites Heimdall and Loki – and grabs the blue space stone, but not before Banner/Hulk whisks away to Earth.

Now in his Banner form, he arrives at Doctor Strange’s Sanctum Santorum and warns Strange, Wong and Tony Stark about Thanos’ impending arrival. Two members of the Black Order arrive in New York to obtain the green time stone – being held inside Strange’s magical necklace, the Eye Of Agamotto – and manage to make off with Strange, with Iron Man and Spider-Man in hot pursuit.

Meanwhile, the Guardians of The Galaxy respond to the Asgardians rescue beacon and meet up with Thor, who takes Rocket and Groot off to create a weapon capable of killing Thanos. The remaining Guardians head to Knowhere to try and stop Thanos from acquiring the red reality stone from The Collector, not realising it is a trap so that Thanos can capture Gamora, the only person who knows the location of the orange soul stone.

Thanos sacrifices Gamora to acquire the orange soul stone, while Iron Man and Spider-Man save Strange and crash on Thanos’ home planet of Titan, just in time to catch up with Star-Lord, Drax and Mantis. The six new friends quickly make a plan to defeat Thanos, who arrives in short order. Thanos beats the hell out of all of them, even crashing a moon into the planet, before acquiring the green time stone from Strange and absconding to Earth.

While all this is happening, Banner has warned the remaining Avengers – including Captain America, Black Widow, Falcon and War Machine – and they collect Vision and Scarlet Witch, then head to Wakanda together to try and save Vision, knowing that Thanos’ goons are on their way to acquire the final yellow mind stone. A huge battle ensues and our heroes look to be on the back foot, before Thor arrives and swings things back in the Avengers’ favour.

But all of that doesn’t really matter because Avengers: Infinity War boasts one of the most audacious – and genuinely stunning – endings in recent blockbuster history. In a nutshell: Thanos arrives in Wakanda, fights our heroes and prevails, then acquires the final stone by killing Vision and snaps his fingers (as predicted earlier by Gamora). The final scene is an extended sequence in which more than half our heroes turn into a cloud of dust and vanish.

It is a heavy-hitting and heart-breaking sequence full of gut-wrenching moments – Peter Parker fighting back tears as he utters “I don’t want to go”, Groot fearfully crying out his infamous line, Tony sitting on Titan covered in the dust left by his young protégé – that left me absolutely stunned. The audience in my screening was dead silent. A few people sobbed.

And then the credits rolled. Brutal.

It’s a scene custom-built to leave the audience hanging for the next twelve months. And I don’t know how many-thousand articles of speculation I’ll read before the next film comes out. Heck, every lengthy conversation I’ve had about the film since I saw it has focused on the ending, and what it means for the universe going forward: how it will play into things like Ant-Man & The Wasp or Agents of SHIELD, how it will be dealt with in Avengers 4, how many (if any) of the deaths will stick.

My gut instinct is not many, if any. It sure looks like Loki, Gamora and Vision might be done, but given some of the names who disappeared in the final scene – including a handful who are confirmed to headline future movies, like Black Panther and Spider-Man – it is hard not to think that Avengers 4 (currently untitled) will deal with the remaining heroes’ attempts to reverse what Thanos did when he snapped his fingers.

And it is kind of a shame, I guess. The ending, as fantastic as it was, only hit so hard because of the build-up, and because of the great character beats we’d just seen for the past two hours or so. Almost every major MCU character of note appears here, meaning the film is packed to the brim with cracking lines of dialogue and team-ups you wouldn’t even think of.

If you want Steve Rogers meeting Groot, or Star-Lord and Spider-Man jumping through Doctor Strange portals and landing hits on Thanos, or Bucky picking up Rocket and using him as a second gun, or Okoye suggesting opening a Starbucks to Black Panther, or Tony telling Banner “dude, you’re embarrassing me in front of the wizards”, you’ve got it.

Iron Man, Thor and Spider-Man are three of the characters who come off best in all of this – especially Stark, whose fears-coming-true approach to this universal threat, and his new power set courtesy of a new nanotech suit, make him one of the most riveting characters in the film. Spider-Man gets a suit upgrade as well, which leads to some of the most jaw-dropping action scenes in the film. And Hemsworth turns in some of his best work – in any film – as he seeks vengeance for the death of his people; a mid-film scene in which he discusses his grief with Rocket is one of the films most moving.

But the MVP here is Thanos; it isn’t a stretch to say that everybody else is a supporting character in this movie about Thanos. Whether he is taking the space stone off Thor, or intimidating the Guardians on Knowhere, or telling Tony that “I hope they remember you” on Titan, or making quick work of the forces in Wakanda, Thanos – as portrayed by Josh Brolin – is absolutely riveting, every bit the universal threat and unstoppable force of nature he was advertised to be.

It isn’t all perfect. The story does jump around a lot, and a lot of characters are underserved; Captain America, Black Widow and Black Panther are three who get relatively little to do here. And I suspect this film is the first in the Marvel Cinematic Universe that will require seeing some, if not all, of the films preceding it. I’d say it is completely inaccessible to new fans.

But when it works, it works perfectly. The Russo Brothers have put together a film that deftly balances over two dozen major characters and nearly half a dozen plotlines, even if it doesn’t always work perfectly, and leaves the audience hanging with one of the boldest endings in superhero film history.

It’s going to be a long year.

Avengers: Infinity War is directed by Anthony and Joe Russo, from a script by Christopher Markus and Stephen McFeely, and based on the comics by Stan Lee and Jack Kirby; it stars (deep breath) Robert Downey Jr, Chris Hemsworth, Mark Ruffalo, Chris Evans, Scarlett Johansson, Benedict Cumberbatch, Don Cheadle, Tom Holland, Chadwick Boseman, Paul Bettany, Elizabeth Olsen, Anthony Mackie, Sebastian Stan, Danai Gurira, Letitia Wright, Peter Dinklage, Benedict Wong, Tom Hiddleston, Idris Elba, Pom Klementieff, Gwyneth Paltrow, Benicio del Toro, Dave Bautista, Zoe Saldana and Chris Pratt, and the voices of Vin Diesel, Bradley Cooper, Tom Vaughan-Lawlor, Carrie Coon and Josh Brolin. It is in cinemas now, clearly.