Ten years of storytelling converge in this film, which follows Thanos as the central character. From the opening scene, he has already won his first victory.
The film begins in the wreckage of the Asgardian refugee ship. Thanos has the Power Stone and has come for the Space Stone in the Tesseract. Heimdall dies sending Hulk to Earth as a warning. Loki attempts one final deception and Thanos snaps his neck. "No resurrections this time." Thor is left floating in space among the corpses of his people.
The Hulk crashes into the Sanctum Sanctorum, where Strange and Wong learn what's coming. Bruce warns Tony. Thanos's children—the Black Order—are already on Earth, hunting the Time Stone and the Mind Stone in Vision's forehead. The war has begun.
The film splits into multiple threads. Tony, Strange, Spider-Man, and eventually the Guardians converge on Titan, Thanos's dead homeworld. Steve, Natasha, and Sam find Wanda and Vision in Edinburgh and bring them to Wakanda, hoping Shuri can extract the Mind Stone without killing Vision. Thor, Rocket, and Groot travel to Nidavellir to forge a weapon capable of killing Thanos.
On Titan, the heroes nearly succeed. They have Thanos pinned with the gauntlet nearly removed when Star-Lord learns that Thanos killed Gamora for the Soul Stone. He loses control, breaks the hold, and Thanos escapes. Quill's grief costs them the advantage.
Strange surrenders the Time Stone willingly. "We are in the endgame now." He has seen 14,000,605 possible futures. They win in exactly one.
In Wakanda, a massive battle ensues with Outriders pouring through the shield while the combined armies of Earth and Wakanda hold the line. Thor arrives with Stormbreaker and turns the tide. Thanos comes personally for the Mind Stone. Wanda destroys it, killing Vision, but Thanos reverses time. He tears the Stone from Vision's head and completes the gauntlet.
Thor buries Stormbreaker in Thanos's chest. "You should have gone for the head."
Thanos snaps his fingers.
Half of all life in the universe dissolves into ash. Bucky. Black Panther. Groot. Wanda. Sam. Mantis. Drax. Quill. Strange. And finally, in Tony's arms, Peter Parker. "Mr. Stark? I don't feel so good... I don't wanna go."
Thanos sits on a farm, watching the sunrise. He has won. The credits roll in silence.