Gotta start with a BIG SPOILER, but one that every last one of you will thank me for. Even though this 181-minute movie comes from Marvel - you know, the folks who love to have an ending, then credits, then another ending, then more credits, and yet another ending - there is no more movie after the credits start this time. So, unless you really need to know the name of the digital matte painter or the assistant costume designer, you can leave when the screen goes black, and shave 10 minutes off that long running time.

Truth be told, the film does feel long, but I can’t think of a frame that I’d remove. Except for a couple of scenes of well-placed, slow-paced gloom, it zips right along. The one occasion I looked at my watch was to note when Stan Lee had what is likely his final cameo: Right at the 100-minute mark, driving a car, in 1970, shouting out an old hippie slogan.

Just mentioning that there’s a scene in 1970 is a hint that “Endgame” jumps around in time. More to the point, it’s a time travel movie in which our heroes try their best to make things that went very badly at the end of the previous entry, “Avengers: Infinity War,” go right in this one.

To sum up that ending, bad guy Thanos (Josh Brolin), making dastardly use of the six Infinity Stones, wiped out 50 percent of all living creatures in the universe, then split for his “retirement” planet. In “Endgame,” kicking off 23 days after that event, our heroes - or what’s left of them on bleak, half-empty Earth - figure that if they can find Thanos and get the Stones back, maybe they can undo what he’s done.

The phrase “things go wrong” could win an award here for understatement of the week. Suddenly it’s five years later and things have gone worse. But this is a movie about smart, good guy superheroes. What, asks one of them, about making use of the Quantum Realm? Or, in layman’s terms, why don’t we invent a time machine, go back and get the Stones before Thanos does, and prevent him from doing what he did?

Of course, they’ve first got to get the band back together again. But Tony Stark (Robert Downey Jr.) is mad as hell at his former compatriots, Bruce Banner (Mark Ruffalo) has converted himself into a Bruce-Hulk hybrid, and Thor (Chris Hemsworth) has gone on a beer-swilling, big-belly bender. At least Natasha (Scarlett Johansson) and Captain America (Chris Evans) are keeping cool heads. But everyone’s a little weirded out by the appearance of the “new girl” Captain Marvel (Brie Larson). Careful readers will note that none of the Guardians folks has been mentioned yet, but worry not, they’re here, in both large and small roles. In fact, I can’t think of a key character from the two franchises that doesn’t show his or her face. There are even glimpses of Robert Redford, Michael Douglas, Tilda Swinton and, thankfully, both Loki (Tom Hiddleston) and Pepper Potts (Gwyneth Paltrow).

With that time travel plot device always at the center, there’s never a question concerning the idea of having some of the characters returning to scenes of earlier Avengers and Guardians films, and seeing themselves in the past. That also means there are accompanying complications, such as what happens when you actually meet yourself in the past.

This is an ambitious movie that’s played out on a gigantic palette and is about people trying their best to believe in the promise of hope. It’s filled with terrible sadness and laugh-out-loud comic relief. There’s no shortage of surprises, with the bigger ones saved for the final hour. It culminates in a spectacular, practically nonstop battle involving as many main characters as could fit on the screen.

And it has an ending, a definitive one that features a couple of major casualties leading up to it. The best part of the whole enterprise is that this is the movie that the Marvel geeks among us have all been hoping for.

Ed Symkus writes about movies for More Content Now. He can be reached at esymkus@rcn.com.

“Avengers: Endgame”
Written by Christopher Markus and Stephen McFeely; directed by Anthony Russo and Joe Russo
With just about everyone from The Avengers and Guardians of the Galaxy films
Rated PG-13