8 months after the events of "Captain America: Winter Soldier", an unstable and erratic Bucky enlists the help of the Avengers to find and liberate a young girl with unknown powers held captive and tortured into submission by Hydra. Meanwhile, a creature begins attacking from the shadows, nearly killing Steve, the result of a mysterious 20 year old Hydra research project.

After falling into the chasm Vanya Romanova and Bucky Barnes are intercepted by the leader of the KGB who used to watch over Vanya as a child. Now dealing with the revelation of who her father is and struggling to get away from KGB to confront her mother there is a lot going on behind the scenes, a deadly enemy from the past is ready for vengeance and it's up to Vanya to stop him.