After the events of Captain America: The Winter Soldier,, the Avengers re-form to hunt down the remnants of Hydra as well as track down the missing scepter of Loki. The trail leads them to the Eastern European country of Sokovia, where they corner Baron Strucker and his troops. But Strucker has a new surprise in store for them – Quicksilver and the Scarlet Witch. Hydra has been experimenting with giving normal humans extraordinary powers and these twins with a grudge against Tony Stark are their first success.
Quicksilver uses super-speed to take out the Avengers, but the Scarlet Witch manipulates their minds to make their worst fears and doubts come true. This has a profound effect on Tony Stark as his fear of an alien invasion is fully realized by the Witch’s powers. After defeating Hydra, this revelation drives Tony to build an artificial intelligence to help the Avengers defend the world. Unfortunately, things don’t go quite according to plan and Ultron is born.