In the weeks following Thanos' (Josh Brolin) snap, which wiped out half of all life in the universe, Steve Rogers (Chris Evans), Natasha Romanoff (Scarlett Johansson), Thor (Chris Hemsworth) and the surviving Avengers on Earth struggle to cope with the aftermath.
Elsewhere in space, Tony Stark (Robert Downey Jr.) is stranded, left adrift with Nebula (Karen Gillan). Unable to move on from the losses, the reappearance of Scott Lang (Paul Rudd) and the arrival of Carol Danvers (Brie Larson) at the Avengers headquarters spark a sense of hope within them.
With that sliver of hope, Steve rallies the remaining Avengers, including Tony and Nebula who have made their way to Earth, for one last mission to do whatever it takes to undo the damage that has been done.