Following Asgard's destruction,[N 1] and having acquired the Power Stone from the planet Xandar, Thanos and his adoptive children Cull Obsidian, Ebony Maw, Proxima Midnight, and Corvus Glaive intercept the ship with the surviving Asgardians to extract the Space Stone from the Tesseract. Thor, Loki and Hulk are powerless to stop them. Heimdall uses the Bifröst to send Hulk to Earth and is then killed. Thanos kills Loki and takes the Space Stone before departing with his children and obliterating the ship.

Hulk crash-lands at the Sanctum Sanctorum, in New York City, where he reverts back to Bruce Banner then warns Stephen Strange and Wong about Thanos' plan to destroy half the universe. After Banner's warning, Strange recruits Tony Stark and briefs him about Thanos and the Infinity Stones. Later, Maw and Obsidian arrive to retrieve the Time Stone in Strange's possession. After a battle including Peter Parker, Maw captures Strange; Stark and Parker pursue Maw's spaceship while Wong remains to protect the sanctum. Banner contacts the other Avengers.

In Scotland, Midnight and Glaive ambush Wanda Maximoff and Vision. Steve Rogers, Natasha Romanoff, and Sam Wilson rescue them, and they take shelter with James Rhodes at the Avengers headquarters. Vision offers to sacrifice himself by having Maximoff destroy the Mind Stone in his forehead to keep Thanos from retrieving it. Rogers suggests they travel to Wakanda and try removing the Stone without destroying Vision.

Meanwhile, the Guardians of the Galaxy respond to a distress call from the Asgardian ship and rescue Thor. Thor surmises Thanos seeks the Reality Stone, which is in the possession of the Collector at Knowhere. Rocket and Groot accompany Thor to Nidavellir to retrieve a weapon capable of killing Thanos, while Peter Quill, Gamora, Drax and Mantis find Thanos at Knowhere with the Reality Stone already in his possession. Thanos kidnaps Gamora, his adoptive daughter, who reveals the location of the Soul Stone to save her captive adoptive sister Nebula from torture. Thanos and Gamora travel to Vormir, a planet where Red Skull, keeper of the Soul Stone, informs him the stone can only be retrieved by sacrificing someone he loves. Thanos reluctantly throws Gamora to her death, granting him the Soul Stone.

Nebula escapes captivity and requests the remaining Guardians meet her on Titan, Thanos' homeworld. Stark and Parker eject Maw from his ship and rescue Strange. They land on Titan, where they meet Quill, Drax and Mantis. Strange uses the Time Stone to view millions of possible futures and tells the others there is only one in which Thanos loses. The group form a plan to confront Thanos and remove the Infinity Gauntlet. Thanos teleports to Titan to retrieve the Time Stone, justifying his plan to Strange as necessary to ensure the continued survival of the universe. The group subdues him until Nebula arrives and deduces Thanos killed Gamora. Enraged, Quill retaliates, which breaks the group's hold on Thanos, and he overpowers them and impales Stark. After Strange surrenders the Time Stone in exchange for Thanos sparing Stark, Thanos departs for Earth.

Thor, Rocket and Groot meet Eitri at an abandoned Nidavellir, and the four create Stormbreaker, an enchanted axe that grants Thor the power of the Bifröst. Back on Earth, the Avengers arrive in Wakanda and task Shuri to safely extract the Mind Stone from Vision. Thanos' army invades Wakanda and the Avengers mount a defense alongside King T'Challa and the Wakandan forces. Thor, Rocket, and Groot arrive on Earth via the Bifröst and rally the defenders. Midnight, Obsidian, and Glaive are killed and their army is destroyed. Thanos' arrival spurs on Maximoff to destroy the Mind Stone, killing Vision, but Thanos uses the Time Stone to undo her actions and personally retrieves the Mind Stone from Vision's forehead, destroying him once again. Despite being severely wounded by Thor, Thanos is able to activate the Infinity Gauntlet and teleport away.

Thanos' plan comes to fruition as people begin disintegrating, including Bucky Barnes, Drax, Groot, Mantis, Maximoff, Parker, Quill, Strange, T'Challa, and Wilson. The surviving heroes are left separated: Nebula and Stark are stranded on Titan; Banner, M'Baku, Okoye, Rhodes, Rocket, Rogers, Romanoff, and Thor remain on the Wakandan battlefield. Thanos, healed, awakens on another planet and watches the sunset in satisfaction.[8]

In a post-credits scene, a distress signal is transmitted by Nick Fury as he and Maria Hill disintegrate along with others. The device displays a red-and-blue star insignia, Captain Marvel's emblem.[9

Haven't seen the movie yet and I don't know if I will but some of the characters who "disintegrate" (according to the synopsis) are already scheduled for future sequels. Way to create suspense. Like... why should I care about the "deaths" of Spider-Man and Peter Quill when there are new Spider-Man and Guardians of the Galaxy sequels coming up?

This movie started off strong! Seeing the Hulk get beat in seconds by Thanos in hand to hand combat was just so impressive and established Thanos as a real threat. Then when you realize that Thanos and his...four horsemen beat Thor and Loki with ease, he really appears to be a scary character.

I don't know why but Thanos' henchmen were super power. They were beating 2-3 avengers at a time and it really had me thinking. If they can't even beat these guys, how are they going to beat Thanos??? With some expert level teamwork, some luck, and plot they managed to take a few wins.

I'm so pissed off at Quill for hitting Thanos on Titan when Iron and and Spider-Man almost had the gauntlet off. They were so close!!! They're plan was also very impressive, I couldn't believe how effective it was. Even with three stones, Thanos was beat. They could have killed him but they chose the high ground and tried to take the glove.

Action was very high in the movie. I felt like I was on edge the majority of the 2+ hours that this movie went on. I was always worrying about who was going to get hurt or if Thanos was really going to get every stone. Who is going to die (please not Spider-Man!!!). I expect the next movie will be a little slower and focus on gathering the strength and devising a strategy to defeat Thanos.

If there was anything I would complain be how easily people gave up the location to an infinity stone or the actual location of an infinity stone. One of the most annoying for me would be Dr. Strange giving up his infinity stone. From the way his character was introduced in his stand alone move and in this one, he would do anything to protect the stone. Dr. Strange is a very logical guy and it doesn't make any logical sense for him to give up his stone.

The last thing I will say is that so many people die/were erased from existence at the end of the movie but many of those characters have movies in development. It ruins the significance of their death for me. Seeing Spider-Man and Black Panther turn to dust bothered me but knowing that Spider-Man is already scheduled to have 2 more movies assures me that he will somehow come back. When Thanos killed Loki, he said something like "there's no coming back this time" and that's something I hope is true. In particular, I don't want Gamora to stay dead but she needs to or else death just continues to be a joke in these movies." I think it's important that real danger exists and that people can die with no way of coming back (that you can lose an eye and never get it back...Thor).

cause those deaths were actually executed extremely well. I knew they’re coming back somehow and that still didn’t stop it from being impactful. The way it’s played out is pretty morbid, and it even ends with it saying “Thanos will Return” rather than saying Avengers or any other Superhero. It’s one of those times where you gotta see it to truly let it hit.

taking the full force of a neutron Star, while holding those rings together to open the hatch for his weapon

For the most part our only remaining heroes are the original Avengers, most of whom end their contract after the next movie. They'll very likely all die while the ones that died at the hands of Thanos this time around will be revived (for the most part, there are one or two I can see staying dead as their plot lines have nowhere left to go.)

Obviously the ones physically killed will likely stay dead, the disintegrations are far less believable however. I will admit though,
Spidey's death shook me hard. Loved the character since infancy and I've never been that taken in by his death or pain before, but Tom Holland has managed to emotionally gut-punch me two movies in a row now, from begging for help under the debris in Homecoming to his fear in this movie.

Vision and Wanda's final moments together also hit pretty hard. Scarlet Witch is one of the few I suspect might stay dead because her character really has nowhere left to go development-wise and she's far too powerful to keep on the field if future threats are lesser than Thanos.

Can someone point me to the spoiler discussing Hawkeye. I'm too lazy to open them all.

Hawkeye, along with Ant man, do not appear in this movie at all. Both are briefly mentioned as taking a deal after the events of Civil War and being under government protection. Chances are both characters will appear in Avengers 4 though.