Full story
In 1995, in a small Ohio town, Natasha and little Yelena live as the daughters of Alexei and Melina, an ordinary couple. It's all a cover: the four are Russian spies. After Alexei steals S.H.I.E.L.D. data, the family flees to Cuba. There, General Dreykov splits them up. The girls go to the Red Room, a program that turns girls into assassins called Widows. Alexei goes to prison in Russia. Years later, Natasha defects to S.H.I.E.L.D. and, with Clint Barton, bombs Dreykov's office in Budapest. She believes she killed the general and his daughter, Antonia.
In 2016, after the events of Civil War, Natasha is on the run for breaking the Sokovia Accords. Hiding in Norway, she gets a package of red gas vials sent by Yelena. On the road she is attacked by Taskmaster, a masked killer who copies anyone's fighting style. Natasha gets away and heads to Budapest, where she finds Yelena after many years, with punches before the hug.
Yelena explains that the gas is an antidote to the chemical control Dreykov uses on the Widows. She herself broke free when it hit her. The Red Room never ended, and Dreykov is alive. Hunted by Taskmaster and the Widows, the sisters decide to find the program's base. Step one is getting Alexei out of a Siberian prison. He was the Red Guardian, the Soviet answer to Captain America, and he loves to brag. The escape, in the middle of an avalanche, is full of laughs.
The family reunites at Melina's farm. She works for Dreykov. Dinner turns into a reckoning over their fake childhood. Melina turns them in, and Natasha and Alexei are taken to the Red Room, a base floating in the sky. It was a plan: the woman they took was Melina wearing Natasha's face, thanks to a mask. On the base, Natasha learns that Taskmaster is Antonia, Dreykov's daughter, who survived badly hurt and was turned into a weapon her father controls. Dreykov uses pheromones so no Widow can attack him. Natasha breaks her own nose to get around it.
The base starts to fall. Yelena releases the antidote and frees the Widows, and Natasha grabs the control unit with the list of every agent around the world. Dreykov dies in an explosion. In free fall, the sisters save themselves with a parachute, and Natasha uses the antidote on Antonia. She gives the list to Yelena, who leaves with Melina, Alexei and the freed Widows to find the rest. Natasha stays behind to face Ross. Weeks later, with blond hair and a new suit, she sets out to break her friends out of the Raft.