In 1959, military men play cards in a laboratory as a soldier brings in a dog for experimentation. The lights around them begin to flicker, similar to a splinter. The men wonder if someone broke in, considering there was no alarm. Before they can do anything, each of the men begin to shift and then disappear, as if they splintered out of time.
In 2016, Cassie stands watch in the hotel room until she hears a movement in the bedroom. She takes her gun and slowly creeps through the dark room. She finds nothing, avoiding a figure of the Witness behind the door. Finally, she injects herself with the splinter formula and returns to 2044.
In 2044, Eckland and Jones play cards in bed, appearing more friendly and comfortable with each other through a small bit of flirting. Eckland jokes that he’s seen Adler looking at her, an idea Jones scoffs at quickly. He then asks if she would have ever re-married if the world wasn’t nearly destroyed, something that gives her pause before denying. The two then nearly share a kiss before the time machine reactivates in bringing Cassie back. Cassie returns to the facility but is, at first, unresponsive as she sees the figure of the Witness in the back. Cole then arrives, bringing her back to her senses.
Meanwhile, Sam shows Ramse a complete model of the facility he had created, including the power connections through the river under the base. Ramse, impressed with the creation, indulges his son by reenacting a splinter sequence with models before he is called back to an intel meeting with Cassie’s return.
Cassie informs the rest of the group about her experience with the Witness in seeing him as Aaron and even feeling his touch. Ramse acknowledges that the Army often drank the tea in order to experience visions and communicate with the Witness, similar to a hallucinogen. Jones theorizes that the tea displaces the mind past the time stream to talk to the Witness, essentially splintering the mind. Cassie maintains that it wasn’t a hallucination since she seemed to have seen the Witness splinter. Jones argues that if the Witness could splinter, he wouldn’t require the use of the time machine to send back the messengers. Otherwise, his abilities remain elusive to them. Jones then asks Cassie if she has any idea why he would want to talk to her. Cassie hesitates to answer, leading Deacon to move her out of the room away from more questions.
In the middle of the night, Cassie takes a drink but then hears another shift. She wanders down the hall to the time machine where she sees the Witness near the machinery. Before she knows it, she’s suddenly back on the floor in the room where she got her drink. Unsure of what happened, she wanders, finding Cole looking at the travel research. He remarks that he’s had trouble sleeping after splinters as well as seeing things. Cole also says that he has seen the way Deacon has acted around her and claims that, although he doesn’t care for Deacon, he isn’t bothered by their relationship. Cassie replies that she didn’t think it would bother him, leading both to see how they don’t seem to know each other as well as they did.
Cole: Tough to sleep after you splinter. Kinda messes with your clock.
Jones and Eckland look back into their research while Cassie continues to train alone. The two attempt to find if there was another traveler in 2016 when they splintered Cassie and manage to find another tether linking back to the facility. At that moment, the machine begins to overpower and spurt blasts of electricity and light across the room. Streams of the time machine’s energy begin reaching across the building, forcing Cole, Ramse, and Sam to move. In another hallway, a wounded creature seems to appear from the blast.
Cassie and Deacon arrive at the center where Jones explains that whatever has happened was a deliberate attack based on rewiring the time machine. Now, the machine will start sending out beams in random directions, threatening everyone on the base. Suddenly, the group is interrupted by a gunshot. The creature appears as a twisted human being now wielding a gun. He shouts that Jones is responsible for what happened to him and moves to kill her. Before he can shoot, the man is killed by Cole who arrives with his own gun. Jones reveals that she recognizes the man as one of the volunteers from the splinter test. He was lost in the time stream during the experiment, emerging from the random blasts of the time machine. Meanwhile, Ramse and Sam try to reach the others as Ramse passes a pile of playing cards in the hall.
Jones explains that whoever was responsible for the sabotage wanted to create a meltdown which would cause a chain reaction across time itself. Cassie recognizes that the Witness wanted to destroy time itself and believes that he was responsible for this reaction. She recalls seeing him near the machine, leading Jones to believe that the Witness was the one connected to the phantom tether. As it is now, Cole and Cassie, despite Deacon’s wishes, leave to shut down the power at its core while Eckland and Deacon attempt to find a replace a part of the time machine to reverse the sabotage. Deacon offers Eckland his gun, but Eckland refuses, stating that he is a pacifist.
In the hall, Cassie elaborates on her experience with the Witness with Cole. She reveals that, after impersonating Aaron, he shifted his form into Cole to try and convince her that his true mission was to stop death. They’re stopped after seeing another grotesque human being crawling on the floor, moaning in pain. Cole puts him out of his misery by shooting the man but finds that Cassie has left.
Elsewhere, Ramse tries to lead Sam to the center while avoiding the new appearances. Suddenly, he is attacked by a vicious dog, the same dog from 1959, forced to let go of Sam. When Ramse finally fights off the dog, he sees that Sam is gone. Ramse then catches up to Cole who finds that his communication with Jones is down, leaving the two on their own.
Eckland searches for a replacement part while Deacon watches his back. He successfully finds one, but the men are confronted by gun shots fired by two other men. These two question what Deacon and Eckland are doing on their army base without permission. Deacon then asks the men about the year to which the figures reply 1959. Deacon offers to explain to them the circumstances for lowered weapons, but the two army men fight back regardless. Deacon fires against them along with Eckland, despite his pacifistic nature. Eckland is shot but successfully re-tosses a grenade thrown by the men, stopping the fight. Deacon helps Eckland back to the center.
Jones explains to Deacon that the facility they work in now was previously a military base, explaining the travelers’ confusion. She helps patch up Eckland but insists on the importance of shutting down the machine with the risk it now puts to the base. With the machine unchecked, the meltdown could turn the facility into a crater. She orders Deacon to find Cole and Cassie who are taken too long shutting down the power.
Deacon: Crater, I understand.
Cassie is revealed to be the one who took Sam, dragging him to the power grid at gunpoint. Cole and Ramse follow her until she barricades herself in the room and points her gun at Sam, preventing them from shutting down the power. In reality, Cassie appears to be trapped in the cabin in the red forest with the Witness controlling her body. Ramse tries to reassure Sam, but Sam secretly points to the floor, reminding his father about the river underneath the base. Ramse then finds an opening through a vent with a fifty-foot drop that could leas inside the room. Cole insists on him going, believing himself to be the best option of reaching to the real Cassie. Using a rope made by nearby wires, Ramse lowers Cole down the vent across to the other side.
With no communication through the base and the machine growing worse, Eckland finds himself with no choice but to change the parts manually, putting himself at risk to the blasts. Jones yells at him to return, believing it to be a suicide mission.
Deacon catches up to Ramse as he sees Cassie holding a boy hostage. He helps lower Cole through the vent, but both he and Ramse are confronted by two remaining members of the 1959 army men. They turn their guns, questioning Deacon and Ramse about the things happening on the base. Not believing the situation, the army men take Cole’s tether and try to pull him back, thinking they are helping him.
Eckland continues to replace the part while dodging blasts from the machine. Jones continues to shout for him to return, but he replies that there is nothing like going out on a romantic gesture for someone you love. Jones shouts back that she doesn’t love him, but Eckland states that she once did, which can never be replaced. He finally replaces the part on the time machine but burns and eventually dissolves from the blast back of the power. This reset of the time machine causes the soldiers to splinter away, allowing Deacon and Ramse to guide Cole into reaching the power core to face Cassie.
Cole tries to appeal to Cassie as she tries to fight her way out of the cabin. Cole urges her to fight if she can hear him, but it appears to be of no use. In their desperation, Deacon calls for Ramse to go after them, saying that Ramse is the only one of the men who could be trusted to kill Cassie. Cole then confronts the Witness holding Cassie hostage and asks him what he has witnessed. As Cassie, the Witness simply replies the end and the beginning. Ramse arrives, forcing her at gunpoint to let Sam go. In the cabin, the real Cassie peers outside a window and sees a massive industrial complex baring the name Titan.
The power core begins rupturing, leaving the group with little time left to argue. Cole finally brings up earlier about how she believed they don’t know each other as well as they did. He argues that it’s not true since she knows him better than anyone, and he her. One thing he knows best about her is that she would never kill Cole or allow him to be killed. Cole then orders Ramse to shoot him as proof. The shock of seeing Cole bleeding on the floor breaks Cassie free as she drops her gun and runs to Cole’s body. In the chaos, Ramse finally shuts down the power core.
Cole: The truth is, I don't think anybody's ever known me like you. And I know you.
However, Jones notices high levels still radiating from the room and shouts for everyone to abandon the power core room. Unfortunately, the power core gives off one final temporal blasts which hits and splinters Sam to the horror of Ramse.
Ramse looks back at Sam’s model of the base and the figure of the time traveler. He asks Jones if Sam is truly dead. Jones replies that she is unsure if Sam is dead, but it is unlikely if he could survive whatever happened or wherever he was sent. However, if Ramse could survive lost in time, his son might have a chance. Nevertheless, Ramse packs his things and leaves the base on his own.
Jones then checks on Cole lying in a hospital bed watched over by Cassie. Cassie informs Jones that with Cole’s healing ability, he should be fine. Jones explains that the phantom tether they tracked was the Witness, but, instead of traveling physically, he merely traveled as an essence, using Cassie’s mind as a receiver. The visions Cassie has been seeing around the base were actually Cassie tampering with the machine under the control of the Witness.Jones believes that she has created an injection to counteract the drug Cassie was given, but even she is unsure if it will keep the Witness out indefinitely. Nevertheless, Cassie still feels an intense guilt over what happened, blaming herself for the deaths of Sam and Eckland as well as Cole being hurt. Jones counters that the only one to blame is her. With that knowledge, Jones knows the way to correct it.
In an indeterminate time, Sam calls out for his father in a forest. He then confronts a figure who leads him away.
Notes from 2044
- The symbol on the water tower marked "Titan" bears the same symbol on Olivia's necklace and tattoo.
- Jones reveals that the base they use for time travel was previously a military base.