The problem they face: if they go into the splinter facility, the causality could screw up everything they've worked for. Undo it all. But Cassie is dead-set on finding Olivia. And there was an arrest in 1971 that Cassie wants to follow up on.
The team decide to sneak into the facility and try to use the machine "one time before the first time." If they can kill Olivia, none of this will have happened, The Witness will not ever have lived. As Cole watches the preparation for his first jump, the gang come up with a plan.
Jones and Cole watch the first jump from above the splinter room. Meanwhile, Cassie sneaks off and stages a fake outbreak that clears the room. While everyone is quarantined, Jones and Cole find their one window to use the machine. Plus, Jones realizes something...
She needs to pay a visit to herself. See, she remembers that the night before she hadn't known entirely how to tether people in these jumps. They finally figure out that what they need is some of the optimism of starting out with the wisdom of being at the end.
Previous timeline Jones learns how to tether from current timeline Jones, and then takes a pill and whiskey to forget everything. (But not before writing down the tether formula.) To her, it's going to feel like a dream.
Jennifer's imaginary friend dies an imaginary death as the Czech police catch up to her. And even though imaginary Jennifer WARNED herself not to forget her passport…real life Jennifer definitely did. Leaving the police with a pretty serious trail of breadcrumbs.
Back in 2043, Jones and Cole realize that the only way to get this mission accomplished is to pose as themselves from that period of time. It goes okay for Cole although it was difficult seeing Ramse alive and unaware of what became of the relationship between he and is brother, Cole.
Finally, they're able to send Cassie Railly to 1971, where she starts her plan to assassinate teenage Olivia before she can bring any havoc upon the world as The Witness. In a rare moment of vulnerability, Cassie begs Cole to come with her but he says no, believing that the mission to kill Olivia is just another dead end.
And finally, back in 2018, Jennifer Goines is cornered by the police at the Prague train station. Jennifer notices the time on a nearby clock and decides to take a terrifying risk, hoping that time is on her side...