Plot
In Malaysia, Yelena Belova destroys a laboratory on behalf of CIA director Valentina Allegra de Fontaine, who is attempting to destroy any evidence of her involvement with the O.X.E. Group’s “Sentry” superhuman project. As de Fontaine faces imminent impeachment for her work with O.X.E. Group, she dispatches Yelena, John Walker, Ava Starr, and Antonia Dreykov—all operatives who have worked for her—to a covert O.X.E. facility with orders to kill each other. In the ensuing fight, Ava kills Antonia while an amnesiac man named Bob is released from a suspended animation pod in the room. After realizing that they were sent by de Fontaine to be incinerated along with any evidence of her misconduct, they work together to escape from the trap. Upon coming into physical contact with Bob, Yelena and Walker briefly experience visions of some of their worst memories.
De Fontaine learns that the group has survived and that Bob was a presumed-dead volunteer in the Sentry trials. When she arrives at the site, Bob creates a diversion by drawing enemy fire, allowing Yelena, Walker, and Ava to escape. Bob sustains no injuries upon being shot, uncontrollably ascends into the air, crash-lands back at the compound, and is captured and transported to the former Avengers Tower in Manhattan, now renamed the “Watchtower”. De Fontaine intends to introduce Bob to the press as a super-powered protector akin to the Avengers, hoping the PR stunt will avert her impeachment. Meanwhile, Yelena’s father-figure Alexei Shostakov, who had overheard details of de Fontaine’s plot while working as a freelance chauffeur, rescues Yelena, Walker, and Ava. Alexei refers to the group as the “Thunderbolts“, in reference to Yelena’s childhood soccer team.
Congressman Bucky Barnes is tipped-off about what has happened by de Fontaine’s assistant Mel. He captures the Thunderbolts and intends to have them testify in the impeachment proceedings. When Mel expresses concern about Bob, Barnes takes the group to New York City to infiltrate the Watchtower. The Thunderbolts discover that de Fontaine has convinced Bob to join her and become the superhero “Sentry”. Bob easily overpowers the Thunderbolts, but he ignores de Fontaine’s order to kill them. He allows them to retreat because he does not see them as a threat. Developing a god-like delusion of superiority, Bob turns on de Fontaine and is stopped by Mel using a failsafe kill switch. This triggers the emergence of the Void, Bob’s destructive alter ego and the embodiment of his depression and insecurities which have been amplified by the Sentry procedure. The Void begins to engulf New York City in supernatural darkness, trapping its citizens in visions of their own traumatic memories.
Realizing that the only way to stop the Void is from within, Yelena enters the darkness to reach Bob’s consciousness. She faces her haunted past as a Black Widow, and finds Bob hiding in a recreation of his childhood bedroom where he hid from his father’s abuse. The other Thunderbolts join them, and together they face off with Bob’s various traumas and drug addiction until they reach his memory of the Sentry procedure in the Malaysia laboratory. They find the Void and are swiftly overpowered. Bob’s attempts to fight back threaten to consume him completely, until the Thunderbolts hug Bob and affirm their belief in him which empowers Bob to regain control and overcome the Void. Light returns to the city and the victims are freed. With the threat of the Void neutralized, the Thunderbolts prepare to apprehend de Fontaine. She manipulates public perception by staging a press conference in which she introduces them to the public as the New Avengers and takes credit for their actions. The group go along with the announcement, but Yelena quietly tells de Fontaine, “we own you now”.
In a post-credits scene set fourteen months later, the New Avengers and Bob discuss a growing feud with Sam Wilson, who has his own Avengers team and is suing the New Avengers for trademark infringement. There is also an ongoing problem in outer space, and the group are interrupted when the Watchtower detects the arrival of an extra-dimensional spacecraft that has a large “4” emblem on the side.