After intercepting a dangerous shipment of nerve gas intended for terrorists, Ethan Hunt (Tom Cruise) embarks on a mission to prove the existence of the notorious Syndicate, an international criminal organization. This shadowy group is believed to be instigating acts of terrorism and inciting upheaval in countries allied with Western interests. Having pursued this lead for over a year, Ethan soon finds himself captured by the Syndicate's operative, Solomon Lane ([Sean Harris]), who traps him in a gas chamber. However, with the aid of the disavowed MI6 agent Ilsa Faust (Rebecca Ferguson), Ethan narrowly escapes a harrowing fate at the hands of another Syndicate member, Janik Vinter ([Jens Hultén]).
Meanwhile, CIA director Alan Hunley (Alec Baldwin) and IMF agent William Brandt (Jeremy Renner) face a Senate oversight committee, where Hunley successfully argues for the disbandment of the IMF, claiming that their reckless actions, including the bombing of the Kremlin, have jeopardized national security. Brandt refutes Hunley's accusations, but the committee decides that the IMF's methods are indistinguishable from happenstance.
With the IMF now dismantled, Ethan follows his only lead: a blond man in glasses who captured him earlier. Hunley further dismisses Ethan's claims, suggesting that the Syndicate is merely a figment of his imagination. Six months later, as Ethan continues to elude capture, Hunley discovers Ethan's research linking government agents who are presumed dead to the Syndicate, along with a pattern of global disasters they are behind.
Desperate for assistance, Ethan enlists the help of former colleague Benji Dunn (Simon Pegg), coordinating their efforts during an opera in Vienna attended by the Austrian Chancellor. As Ethan attempts to neutralize an assassin targeting the Chancellor, tragedy strikes despite their efforts, leading to the Chancellor's assassination via a car bomb. Ethan helps Ilsa escape the chaotic aftermath, and they begin to share secrets, with Ilsa admitting that her previous actions put her in a precarious position.
As Ethan tracks down the mysterious blond man, it becomes clear he is Solomon Lane, the mastermind behind the Syndicate, who aims to retrieve a ledger containing the names of all his operatives. With the help of Benji, Ethan formulates a plan to infiltrate a secured underwater server in Morocco, which holds critical information regarding the Syndicate's global network.
Despite successfully acquiring the data, Ilsa is forced to betray Ethan to regain the trust of her superiors within MI6. Unbeknownst to them, the drive falls into Lane's hands, revealing an encrypted "red box" containing state secrets requiring government approval to unlock. With the clock ticking, Ethan realizes that Lane's plan involves abducting the British Prime Minister.
As events unfold, Ethan infiltrates a charity auction posing as a government official, aiming to thwart Lane's sinister design to capture the Prime Minister. In a high-stakes encounter, Ethan reveals the Syndicate's existence and the secretive operations that Lane hijacked. Knowing that the information is of great monetary value rather than tactical, Ethan decides to destroy the file, forcing Lane to negotiate for the release of his captured friends.
The film culminates in a thrilling chase through the streets of London, where Ethan and Ilsa confront Lane, ultimately leading to Lane's capture in a twist of poetic justice—the same method he employed against Ethan. In the aftermath, the IMF is reinstated, and Ethan's resourceful determination is rewarded, as Brandt commends Hunley for his newfound understanding of the team's mission. As the credits roll, the IMF prepares to return to the field, ready for new challenges ahead.
