In front of the smoking rubble of the Vancouver Police Headquarters, Kiera asks Carlos for one last favor: to give her a head start before Carlos launches his assault on Kellog's facility. Kiera meets up with a contemplative Alec, urging him to help her stop Kellog's army and validate the deaths of everyone who's tried to stop it so far. Alec reminds her that he's still not sure that, even if he can send her into the future, just what kind of future he will be sending her to. Knowing this, Kiera is still willing to risk everything for the chance to see Sam again.
Brad delivers the device key at Kellog's facility and the portal is activated. The portal tethers to a point in the future to bring over Kellog's army, allowing them ninety minutes to bring everyone through the portal. A trio of future soldiers rush through, but something is wrong. Zorin orders the portal to be shut down as Weaver discovers that the device key has shorted.
At Alec's apartment, Jason packs up the hidden copy of the Time Ball and scribbles a note for an unknown reader, mumbling, "it's for the best," as he leaves. At PIRON headquarters, Chen strolls into Kellog's empty office and takes Kellog's copy of the Ball from his safe.
Kellog tries yet again to woo his bodyguard-turned-captor, Vasquez. Meanwhile, Zorin informs Kellog that their two timelines are now tethered, and what happens to Future Kellog happens to this Kellog. Vasquez reveals the ugly truth about what Future Kellog has in store for this current Kellog - a paradox that threatens to jeopardize his current timeline's own life to save the ailing Future Kellog.
Carlos gives Kiera a half-hour head start before the assault on Kellog's facility. They exchange a heartfelt and tearful farewell. Kiera assures Carlos that he's a good man. Before Kiera can drive away with Alec, Dillon stops her, demanding to know answers about why they've been covering for Travis. Kiera shows him her service weapon and reveals that she, Liber8, and Kellog's army are all from the future. Dillon is stunned as Kiera drives off. Garza watches from a distance.
Back at the facility, Kellog paces like a caged animal. He lays on the manipulation act as thick as he can for Vasquez, who becomes increasingly more uncomfortable with his advances. After a final rebuff, Kellog stabs her with a corkscrew from a table of lavish foods. As she dies in his arms, Kellog learns the horrible truth about why she could never be with him: Vasquez is his daughter. Horrified, Kellog makes his escape.
Alec and Kiera meet up with Jason, who hands over the Time Ball to Alec. Kiera offers to take Jason with her, but he politely refuses, offering that he's been in this timeline too long and he belongs here now. The cryptic note he wrote is a message for his father in 2077: just some things he never had a chance to say when he was there last. Kiera says her goodbyes to Jason and heads for the facility with Alec.
A blood-stained Kellog meets with Chen and one of PIRON's guards, who turns over the Time Ball to Kellog. He calls Kiera and tells her to meet them at a secure door in the facility.
Down by the malfunctioning portal, Weaver struggles to get the portal back online as Brad demands answers from Zorin: specifically, if Marcellus knew about the invasion. Zorin reveals the truth that Brad has feared all along: Marcellus played him like a fiddle. Brad is infuriated.
As they prepare to enter the facility and launch into their plan full of unknowns, Alec offers Kiera a deeply sincere thanks for all the ways she's changed his life for the better and vows not to let her down. Kiera and Alec meet Kellog as they each debrief each other on their immediate next steps in the plan. Before they head into the portal room of the facility, Kellog offers a maudlin goodbye to Kiera, who has no kind words to offer in return. Before she can make her way there, they are stopped by Brad, with his gun drawn.
Jason meets Carlos at the assault base camp outside the facility and warns Carlos that they have a literal ticking time bomb inside the building that could level half the city - thus buying Kiera and Alec more time.
Kiera reminds Brad that as time travelers, they're all just pawns. As he lowers his gun, he reveals that Marcellus had lied to him from the beginning and that it was always going to be a full-scale invasion. When Kiera asks him what he wants to do about it, he says simply that he wants to prevent more suffering. In that moment, Kiera reaches her own moment of sobering clarity and vows to destroy the machine and the portal, sacrificing her own mission home. Kellog makes his exit.
As Carlos and his team rolls up to the secure entry point at the facility, Dillon joins the fight. Garza disables a guard and grabs a gun for herself and enters the facility as well. Carlos, Dillon, and the team make their way into the main portal room as Kiera and Alec sneak their way in, with Brad providing cover. He informs Zorin that Vasquez is dead and Kellog is missing. Zorin sends Grimes (one of the trio of future soldiers who just came through) to find Kellog; he also hands Weaver one of the power cells.
The assault begins as Zorin spots Carlos. Weaver runs out wearing one of the super suits and begins firing mercilessly at Carlos and his team. Meanwhile, the PIRON guards supporting Carlos don't shoot back - on Kellog's orders. Kellog emerges across the facility, heading for the portal. Carlos and Dillon double back to stop Kellog. Kiera grabs Kellog at gunpoint. She reveals Kellog's master scheme all along: knowing that his future is doomed, Kellog planned to use his Time Ball to travel back into time when Liber8 and Kiera first arrived in 2012 - and kill them all, wiping the slate clean for himself. Grimes sneaks up and puts a gun to Alec's head.
Weaver, in the super soldier suit, continues to decimate the assault team. Zorin orders Alec to repair the portal key while Grimes continues to hold him at gunpoint. Begrudgingly, Alec does it. Weaver powers down the super suit and returns the power cell back to the machine. Before Zorin can activate the portal, Brad tackles him as Carlos and Dillon make their way over. A heavy firefight ensues.
As Kellog takes cover, he pieces together the Time Ball as Weaver activates the portal. The future army is ready and waiting. When Dillon tries to stop Kellog from approaching the portal, Kellog shoots Dillon multiple times in the chest. Kiera runs to Dillon's side. As Kellog stands on the precipice of the portal, he shouts back to Kiera: "I choose me!" and steps into a point in time unknown. Kellog's army vanishes as a result of the paradox of Kellog stepping through the portal. The portal begins to collapse.
As Dillon lays dying, Alec tells her that it's now or never for her chance to head forward into the future. Kiera is torn, unwilling to leave Dillon's side as he dies from his wounds. Kiera tearfully accepts the Time Ball from Alec, who promises to build Kiera a better world. Kiera stands at the intersection of past, present, and future in front of the portal and casts one last glance at the world and time she is about to leave. Chen and Garza look on as, before Kiera steps into the portal, the Traveler appears. The continuum is righting itself.
Kiera vanishes through the portal to a fate unknown as Carlos orders everyone to fall back.
Outside the facility, Garza questions if Kiera is dead. Alec doesn't know for sure. Brad notes that Kiera was tethered to his future, but Chen counters that Brad's future was destroyed when Kellog entered his own timeline. With few answers and only more questions, everyone will have to wait another sixty years to find out what happens to Kiera - and posits a challenge to build a better world for Kiera. When Garza brings up Kellog, Alec reveals the failsafe that he and Kiera cooked up beforehand, by reverse engineering Kellog's time ball to send him much farther back into the past than he originally planned.
Meanwhile, in a lush green forest hundreds of years in the past, Kellog looks around, orienting himself. Tribal peoples with spears drawn surround Kellog, who comes to the unsettling realization of his now doomed fate, cursing Alec in the process.
In the future, Kiera appears at the feet of Eduoard Kagame inside a massive building. She backs away from him in horror, claiming Liber8 won - but Kagame doesn't seem to understand. He recounts the tales his Uncle Julian once told him about the evil corporations, and then realizes that she's Kiera. An aged Alec Sadler - the familiar face of the once Future Alec - comes bounding down the stairs. With joy in his voice, he exclaims, "it worked!" as he reveals that he's been waiting sixty years to find out what happened to her. Kiera is in disbelief and throws her arms around him. She immediately asks about Sam, and Alec offers to take her to him.
As they stroll through the Carlos Fonnegra Memorial Park, Alec shares all that has happened in the last sixty years that Kiera was gone: Alec spent all his days with Emily until she died, there was no societal collapse and CPS never needed to be formed. There was no Corporate Congress, thanks to Alec, Julian, and Kagame's combined efforts. Relieved and overjoyed at the future Alec helped to create because of her, Kiera goes to see Sam playing by a fountain in the park, but Alec stops her.
Alec explains the dark truth of their efforts, the price paid for making the world a better place: Kiera can never be with this Sam, because his mother is the Kiera Cameron of this timeline - and the Kiera that stepped through the portal is now a relic of a future that no longer exists. As Kiera reels from the realization that Sam will grow up in a world without violence or corruption - but without ever truly being with Sam ever again - Alec reassures the bewildered Kiera that she will understand the price of real love ... in time.