In 1985 Mexico City, Heinrich Treadway (Dylan O'Brien) tries to escape the authorities and a man, Bathurst (Rupert Friend). He and his associates, Abel (Tom Hughes) and Leona (Joana Ribeiro) speak about "the Egg," which Treadway stole from Bathurst. Treadway tells Abel that if he does not survive, the latter must remember to "look inside". He drives off a bridge, jumping from his car in mid-air and onto a crane 150 feet away. However, Treadway watches helplessly as Bathurst arrives and kills Abel and Leona.In 2020, Evan McCauley (Mark Wahlberg) suffers from schizophrenia. Because of past institutionalization and violent behavior, he cannot get a job. Needing medicines, he forges a Katana for a local gangster, even though he was never trained as a blade-smith. After the deal goes south (client is a psychopath and tries to cut the hand of his prostitute to test the Katana, forcing Evan to intervene), Evan makes his escape but is later arrested. A man at the police station introduces himself as Bathurst (Chiwetel Ejiofor). He starts to refer to Evan as Treadway and claims they have known each other for centuries. Bathurst shows a lot of items to Treadway from his past lives, in a bid to revive his memories.When Bathurst gets Evan to remember things about his past life, a car slams into the room. Evan's rescuer is Nora Brightman (Sophie Cookson) (who manages to shake off Bathurst in a car chase), who takes Evan to the group she is part of. Bryan Porter (Toby Jones) is the Director of Operations and helps Nora in her field ops. There are about 500 individuals in the world who can remember all their past lives, known as the Infinites. Two opposing factions have developed among the Infinites: The Believers and the Nihilists. The Believers, such as Nora, think remembrance is a gift bestowed on them by a higher power in order to make the world better. Nihilists like Bathurst consider it a curse. They think the Infinites are condemned to witness humanity self-destruct. They want to be free of this (cycle of reincarnation) and exterminate all life on Earth.Both factions believe that Evan is Treadway's reincarnation. Hidden in his memory of his past life is the location of the Egg, the device that was created to end the world (it attacks the DNA of every living thing on the planet. If nothing is alive, there is nothing to reincarnate into) (In his past life, Treadway attacked Bathurst's lab and stole the egg, and killed his Einstein, leaving him no way to recreate it). The Believers must retrieve his memory and secure the Egg before Bathurst gets Evan and tortures the information out of him. As Nora, Leona's reincarnation, explains to Evan, the Infinites start to remember things when they are young. By puberty, they have recalled everything. This is why Evan was diagnosed schizophrenic. Meanwhile Bathurst finds Bryan's location in NYC and attacks him. He brute forces his encryption to find the location of Evan. Bathurst kills Bryan with a Dethroner, which destroys the memories (by downloading them into a digital chip) and stops the reincarnation.Despite their progress, Evan struggles to regain Treadway's memories, revealed to be the result of trauma endured from accidents earlier in life (which left a steel plate embedded in his head). Nora decides to take Evan to the Artisan in London, and shortly thereafter Bathurst attacks the Believer's home base, but finds nothing. However, after a session inside Artisan's (Jason Mantzoukas) machine, Evan unlocks his memories.Treadway was killed by the previous Bathurst not long after Abel and Leona. The Believers retrieved his body and took it back to the Hub, where it is kept in a chamber. Evan recalls that he had slashed open his belly and put the Egg inside. Bathurst used to be a comrade of Treadway. They spent centuries fighting beside each other. However, Bathurst became disillusioned with the Believers' mission and began attempting to end the reincarnation. The Egg was the product of that search. When activated, it will attack the DNA of living beings and destroy life. Bathurst spies on the Believers and now knows that the egg was hidden inside Treadway's body from his previous life. Bathurst attacks the Artisan's facility, but Treadway and Nora manage to escape as Kovic (Jóhannes Haukur Jóhannesson) stays behind to fight the Nihilists and give them a chance to get away.Bathurst then returns to the Hub and retrieve's Treadway's previous life's body and transports it to Scotland. He finds the Egg inside the body, as expected. Nora attacks Bathurst's HQ but fails to kill him. Evan was injured in the previous attack and was being treated by the Artisan. He follows Nora, to join the fight. Nora and Evan join forces to attack Bathurst's HQ, where he prepares the Egg for launch. As Evan gets near, Bathurst gets on a plane with the Egg and Evan follows him. Bathurst shoots Evan with the Dethroner, but the bullet hits the steel plate in his skull, giving Evan the chance to counterattack. In the ensuing fight, the device with the Egg inside it flies out of a plane. Evan jumps after it and Bathurst follows. The two fight in mid-air, and Evan manages to stop the countdown by pulling out the Egg. He shoots Bathurst with a Dethroner, which ensures that Bathurst will not be reborn. Evan drowns in the ocean with the egg. Meanwhile Nora and the Artisan destroy the chips freeing the souls of the Believers Bathurst trapped, including Abel's.Years later, Nora and Abel are reborn, and they meet at the Beginning. Evan is reborn in Jakarta, Indonesia. Artisan, now older, visits him and offers a Katana to the younger Evan, who regains his memories upon recognizing him.