A formidable alien race known as Mimics has taken control of continental Europe. Responding to this grave threat, General Brigham (Brendan Gleeson), the leader of mankind's United Defense Force, orders Major William Cage (Tom Cruise), a public affairs officer with a background in advertising, to document the upcoming assault on the Mimics along the beaches of France. Cage, however, protests against this perilous mission, vehemently declaring that he will utilize his PR skills to sway public opinion against Brigham once the casualties begin to mount. His defiance leads to his arrest and subsequent awakening in handcuffs at a forward operating base at Heathrow Airport, where he learns that he has been categorized as a deserter and assigned to combat duty as a private under Master Sergeant Farell (Bill Paxton) for the imminent invasion.
The assault turns into a catastrophic failure for the human forces. In a desperate attempt, Cage manages to eliminate a significant Mimic but meets his demise as he is doused with its corrosive blood. To his astonishment, he then awakens at Heathrow the very next morning, confronted by disbelief from his peers regarding his claim of foreknowledge about their impending defeat. Caught in a relentless cycle, he dies repeatedly on the beach and subsequently wakes back at Heathrow until he crosses paths with Sergeant Rita Vrataski (Emily Blunt), who recognizes his unique capacity to predict upcoming events. She advises him to seek her out the next time he "wakes up."
Once Cage finds Vrataski at Heathrow, they enlist the help of Dr. Carter ([Noah Taylor]), an erstwhile government scientist skilled in Mimic biology. Cage discovers that the Mimic he killed—an "Alpha"—grants him the power to reset time whenever it is eliminated. This transformative ability was passed to him when he was splattered with the Alpha's blood during their mutual fatal encounter. Vrataski shares her own experience, revealing that she previously possessed the same gift during a different battle at Verdun but lost it after receiving a transfusion. She elaborates on the strategic maneuver employed by the Omega, the Mimics' command entity, which sought to instill false confidence in humanity by allowing Vrataski to secure a victory at Verdun, thus luring them into a misguided invasion of France.
Understanding that they must locate the Omega to dismantle its hive mind, Vrataski instructs Cage that he must continue to die daily until that crucial day arrives. Furthermore, Dr. Carter warns Cage that the Omega has lost its ability to reset the day for him and will be actively searching for him. As time cycles continue, Vrataski diligently trains Cage to become a more formidable warrior. Following moments of despair during these loops, Cage ventures to London, where he uncovers a plot by the Mimics to overrun the city amidst the beach invasion. Together, Cage and Vrataski dedicate numerous loops to mastering their survival tactics in hopes of utilizing his visions to locate the Omega, which they suspect is hiding within a dam in the Bavarian Alps.
After countless loops lead to devastating results, including Vrataski's untimely death, Cage resolves to pursue the Omega alone, leaving her and the rest of the invasion to face doom on the beach. Upon reaching the dam, he finds that the Omega is absent and, in a last-ditch effort, takes his own life before an Alpha can capture his blood and disrupt his time-resetting ability. Back at Heathrow, Cage informs Vrataski and Carter that his earlier vision was a ruse.
In a bold new strategy, Cage and Vrataski infiltrate the Ministry of Defence to locate a prototype device created by Carter that will enable Cage to pinpoint the Omega's true location. This groundbreaking transponder is capable of revealing the Omega's whereabouts once it is attached to an Alpha. After enduring a series of unsuccessful attempts, they finally secure the device from General Brigham, only to discover that the Omega is situated beneath the iconic Louvre Pyramid in Paris. During their escape, they sustain injuries, and Rita's inability to terminate Cage this time due to his condition is a pivotal moment. Although Cage's life is spared through a blood transfusion, it unfortunately strips him of his day-resetting power.
With newfound determination, Vrataski frees Cage, and they return to Heathrow to rally his squad for a mission to annihilate the Omega. They instruct the team not to kill any Alphas, as doing so would enable the Omega to reset the day and anticipate their attack on the Louvre. In a valiant sacrifice, the squad members give their lives to ensure Cage and Vrataski can reach the heart of the Louvre. As the conflict intensifies, Vrataski distracts a waiting Alpha while Cage stealthily moves in on the Omega. Ultimately, both fall victim to the Alpha's attack, but not before Cage successfully plants a grenade belt within the Omega's core, leading to its explosion and the subsequent neutralization of the Mimics.
Cage's body, in a surprising twist, absorbs the Omega's blood, granting him a final awakening en route to his meeting with General Brigham, mere moments before the attack on the Louvre. Brigham conveys the shocking news that Mimic activity has ceased following a surge of power in Paris. This turn of events prevents Cage from being arrested, allowing him to return to Heathrow where he encounters his squad mates, including Farell. Strikingly, they no longer recognize him, treating him with the esteem due to a Major. His final meeting with Vrataski is bittersweet, as she too fails to acknowledge him, inquiring what he desires—echoing their previous encounters—and this time, Cage responds with a knowing smirk and a laugh.
