A powerful and unforeseen evil force emerges, posing a lethal threat to Earth that no single superhero can withstand. S.H.I.E.L.D., the organization dedicated to protecting global security, finds itself overwhelmed. Their commander, Nick Fury "The Eye" Fury, realizes he must create the "strongest alliance" in history, gathering heroes from all walks of life to save the world from destruction and combat the forces of darkness.

Tony Stark attempts to restart a defunct peacekeeping project, which becomes the catalyst for a new crisis. The mysterious villain Ultron emerges, forcing the Avengers to reunite and work together to prevent Ultron's plan for human extinction. During the battle, the Avengers encounter two new characters - Wanda Maximoff (Scarlet Witch) and Pietro Maximoff (Quicksilver) - and welcome back an old friend in a new form: Vision.

Thor and his team are the first to encounter Thanos' army, suffering devastating losses as Loki dies and the Space Stone falls into Thanos' hands. Soon, Thanos' advance forces arrive on Earth, engaging in battle and capturing Doctor Strange after a fierce fight. An epic battle that will determine the fate of the entire universe unfolds, as superheroes fight relentlessly for ordinary yet free lives in their ultimate confrontation with Thanos.

A snap of fingers, and half of all life in the universe turns to dust. The nearly despairing Avengers find Thanos' hideout with Captain Marvel's help, only to learn that all six Infinity Stones have been destroyed, crushing their final hope. Five years later, Ant-Man, lost in the Quantum Realm, accidentally returns to the real world, his appearance reigniting hope for the surviving Avengers. A final battle destined for the history books unfolds as superheroes fight relentlessly for their beliefs.