Mac investigates a mass arrival of Travelers, while also trying to repair his marriage with Kat. Philip is given assistance with his addiction from fellow Traveler 4514, Jenny. Marcy treats David for PTSD, but is dealing with feelings of detachment and disassociation herself. Carly and Jeff try and clean up their act for Child Protective Services and regain custody of their son. Trevor and Grace bond in the hospital while recovering from their injuries.
Once a sleepy second fiddle to Southern culinary powerhouses like Charleston and Nashville, Greenville is stepping into the limelight with hot new restaurants. The town will soon be home to an outpost of Sean Brock's heirloom-crop-focused Husk and a food-centric market hall called the Commons. Other recent additions include modern Italian spot Jianna from Michael Kramer (the opening executive chef of McCrady's in Charleston, pre-Brock) and the moody speakeasy lounge Vault & Vator. It's an impressive collection of quality restaurants for a city of just over 67,000.
Three high-ranking Travelers are sent back by the Director to put Grace on trial for violating protocols, overwriting a person who was not assigned to be her host, and sabotaging the Grand Plan. Mac and the team must give testimony at the trial that will determine if she should be overwritten or not. Meanwhile, the Faction is trying to replenish its numbers by overwriting people with the stored minds in the Quantum Frame. It transpires the trial was staged by the Director to flush out a Faction member from within the three Travelers judging Grace, which it successfully does, this leading to Mac's team securing the Quantum Frame.
Travelers transfer into a cult preparing for mass suicide. MacLaren's team, the cult, and many other travelers, including senior engineer Bloom, meet at the antimatter facility. Bloom reveals that the future has been subtly rewritten and is not as united as it once was. Dosed with antitoxin, they release a toxic cloud to force a local evacuation. Gleason interrogates Delaney until MacLaren returns her to the facility and explains the nature of travelers. Gleason discovers Delaney's escape and prepares to return to her lab. Using the antimatter to power an x-ray laser, the travelers intend to deflect asteroid Helios 685, saving millions of lives and preventing the environmental catastrophes and devastating wars that led to their dark future. Deflecting Helios has been the Director's main goal, even though it could possibly prevent the travelers' own births in the future. Gleason leads an assault, killing most of the cult travelers and Bloom before she can fire the laser. However, travelers transfer into his soldiers and eventually into him, sacrificing themselves to complete the mission. The traveler within Gleason fires the laser while MacLaren and his team save Delaney from the antimatter explosion on Bloom's orders. MacLaren is unsure of the mission's success, as his team remains in the present.