Synthetic olfactory neutralization gas is becoming real

In 1995, super soldier Alexei Shostakov and Black Widow assassin Melina Vostokoff work as Russian undercover agents, posing as a family in Ohio with Natasha Romanoff and Yelena Belova as their daughters. They steal S.H.I.E.L.D. intel and escape to Cuba where their boss, General Dreykov, has Romanoff and Belova taken to the Red Room for training as Widows. In the following decades, Shostakov is imprisoned in Russia while Romanoff and Belova become successful, dangerous assassins. Romanoff eventually defects to S.H.I.E.L.D. after helping Clint Barton bomb Dreykov's Budapest office, which apparently kills Dreykov and his young daughter Antonia. In 2016, Romanoff is a fugitive for violating the Sokovia Accords.[b] She escapes from U.S. Secretary of State Thaddeus Ross and flees to a safehouse in Norway supplied by Rick Mason. Meanwhile, Belova kills a rogue former Widow but comes in contact with a synthetic gas that neutralizes the Red Room's chemical mind-control agent. Belova sends antidote vials to Romanoff, hoping she and the Avengers can free the other Widows, and goes into hiding. When Romanoff is unknowingly driving with the vials in her car, Red Room agent Taskmaster attacks her. Romanoff escapes from Taskmaster and realizes that the vials came from Budapest. There she finds Belova, who reveals that Dreykov is alive and the Red Room is still active. Widows and Taskmaster attack them, but Romanoff and Belova evade them and meet with Mason, who supplies them with a helicopter. Romanoff and Belova break Shostakov out of prison to learn Dreykov's location, and he directs them to Vostokoff, who lives on a farm outside Saint Petersburg. There she is refining the chemical mind control process used on the Widows. Vostokoff alerts Dreykov and his agents arrive to take them, but Romanoff convinces Vostokoff to help them and the pair use face mask technology to switch places. At the Red Room, a secret aerial facility, Vostokoff frees Shostakov and Belova from their restraints. Dreykov sees through Romanoff's disguise. He reveals that Taskmaster is Antonia, who suffered damage in the Budapest bombing that was so severe Dreykov had to put technology in her head to save her. This turned Antonia into the perfect soldier, capable of mimicking the actions of anyone she sees. Romanoff is unable to attack Dreykov due to a pheromone lock installed in every Widow, but negates that by breaking her own nose and severing her olfactory nerve. Shostakov battles Taskmaster while Vostokoff disables one of the facility's engines, and they then lock Taskmaster in a cell. Dreykov escapes as other Widows attack Romanoff, but Belova exposes them to the antidote. Romanoff copies the locations of other Widows worldwide from Dreykov's computer as the facility begins to explode and fall. She retrieves two surviving antidote vials and frees Taskmaster from the locked cell. Vostokoff and Shostakov escape via a plane while Belova blows up Dreykov's aircraft, killing him. In freefall, Romanoff gives Belova a parachute before battling Taskmaster. After landing, Romanoff uses one antidote vial on Taskmaster and gives the other to Belova along with the locations of the other mind-controlled Widows so she can find and free them. Belova, Vostokoff, and Shostakov say goodbye to Romanoff and leave with Antonia and the freed Widows. Two weeks later, Mason supplies Romanoff with a Quinjet to use in freeing the imprisoned Avengers.[b] In a post-credits scene set after Romanoff's death,[c] Valentina Allegra de Fontaine visits Belova at Romanoff's grave. De Fontaine blames Romanoff's death on Barton and assigns him as Belova's next target.