In the fictional nation of Sokovia, the Avengers infiltrate a Hydra facility led by Baron Strucker, where they encounter the super-powered twins, Pietro and Wanda Maximoff. They capture Strucker and retrieve Loki's scepter. Tony Stark and Bruce Banner use the scepter's advanced AI to create "Ultron," but it goes rogue and seeks to eradicate humanity.
Ultron upgrades himself, recruits the Maximoff twins, and searches for vibranium. The Avengers hide at Clint Barton's farmhouse. Thor consults with Dr. Selvig about a troubling vision. Nick Fury urges them to stop Ultron.
Ultron forces Helen Cho to create a new body. The Avengers, aided by the Maximoffs, recover the body and create Vision. They confront Ultron in Sokovia, where he plans to cause global extinction. The Avengers have to sacrifice a lot to overcome this mighty villain.