As the sin fog sweeps the town, Nancy, Nick, Bess, George, and Tristan head to the Historical Society. Once there, they find Callie has left town. Bess says she got a lead on how to fight the sin fog. The sin eater's soul may be powerful enough to combat sins in multiple bodies. It is only the sin eater's physical body limits how much it can consume. If they can harness the sin eater's soul from Tristan and make a sin eater supernova, it could cure everyone in town all at once.

Nancy worries about what it might do to Tristan, but he wants to do this. He finally feels in control.

In town, Red and Carson are infected with the sin fog and begin stealing from local shops. There's nothing Ryan can do to stop them.

The townspeople start yelling, "Find the witch!" They head off to find Bess at the Historical Society.

Jade refuses to leave Horseshoe Bay if Nick won't. Nancy asks her to find Carson. Nick tells George that his canceled road trip with Jade was also about seeing where else they might want to live someday.

George has an interview with the alumni from Northern Seattle Legal College. When they ask about her educational accomplishments or lack of them, George tells them she's worked 12 hours days at The Claw, followed by four-hour pre-law lectures and two-hour study sessions while being mentored by the county’s best lawyer and managing town-wide emergencies. If that’s not enough for their school, then their school is not enough for her.

In speaking with Nick, Ace shares that he doesn't think he can ever forgive Nancy for trying to erase what he did to Alice. Nick reminds him that if he hadn't been forgiven for the worst day of his life, he wouldn't be here with them now.

sWhen they try to release the sin eater's soul from Tristan, Nancy is the one who collapses. She sees visions from the past of many people, but they all feel like her. Like she was them at one point.

Bess reads that one phenomenon that could halt the supernova is if another soul is entangled with the sin eater's. Nancy recalls Nashua telling her they'd walked this path many times before. Tristan theorizes that they may be soulmates.

They realize that all of Nancy's visions are from the same place, just different times. They assume that must be the spot where she and Tristan's souls became entangled.

Nancy feels something in a particular spot in town. There's a crawl space beneath it. They find the silver scissors from Nancy's visions. They have the name Lucia Kipp engraved on them. She was Nashua's wife. They were tailors. They deduce that Nancy may have once been Lucia. With the soul residue on the scissors,

Bess can disentangle Tristan and Nancy's souls. But it's dangerous. It's using a metaphysical force that can burn Nancy's soul away from Tristan's, but it could also be fatal. And they need a piece of Lucia Kipp's remains to do it.

Also, Nancy and Tristan must be on the brink of dying of this to work. Bess has a supernatural poison for that. And they need a third person to go into the mystical realm to bring them back. Ace volunteers. Nancy tells him it's too risky. But Bess says that since the death curse links Nancy and Ace, Ace will be able to find her, making him the perfect person to help.

During the ritual, Nancy, Tristan, and Ace can all see Nancy's past lives. They witness a fight between Nashua and August Pritchard, the Horseshoe Bay founder who stole Nashua as a child and turned him into the first sin eater.

Nashua wanted to stop August and killed him with Lucia's scissors. That's when they learn that Nancy's former soul isn't Lucia's but August's. Her soul and Nashua's didn't entangle because of love but vengeance. In the mystical realm, Nancy realizes that her past life is the source of the darkness that haunts Horseshoe Bay.

Tristan follows her while Ace goes back to reality to tell Bess. Then Lucia's DNA won't work to break the entanglement, and August Pritchard's body was never found.

Nancy realizes that Nashua couldn't stop August by killing him since August had already sent sin eater instructions up and down the East Coast.

Realizing what Nancy is going through, Ace tells her he forgives her.

They learn that August was buried at Dead Man's Bluff, the same place where Lucy gave birth to Nancy. But the mob turns up at the Historical Society. They are possessed by previous townspeople who had burned a witch's house down while she was still inside.

During the ritual in the other realm, Tristan is freed, but Nancy's soul is damaged. Ace has to pull her out. Nancy tells him to leave, but Ace refuses to leave without her despite the risks.

The mob comes to burn the Historical Society. Nick and George get Tristan out before the supernova, but Bess stays inside with Ace and Nancy since they are still in the mystical realm.

Nick tries to stop the mob, but they throw a torch through the window, setting the house on fire with Bess, Ace, and Nancy inside.

Ace and Nancy return from the mystical realm just in time for Bess to lead them from the burning building. Tristan becomes the supernova that breaks the curse, but all the Drew Crew can do is watch the Historical Society burn to the ground.

Nick wants to save what's inside, but it's too dangerous. The Drew Crew has to physically restrain him from running back into the fire. Bess tells him he doesn't owe this town anymore.

Afterward, the news reports that toxic mold in the water supply sparked the violence. Addy tells Bess that Chief Lovett is moving any artifacts that survived the fire to the underground historical society.

They all leave flowers at the reburied sin eaters' graves with their new gravestones and promise to never stop telling the truth about the sins they were forced to consume.

Tristan tells Nancy that her soul has grown and changed since it was August's. That's why Nashua met her as a friend and not an enemy. Nancy has to own her past lives to help heal this place. There are many sin eaters out there, and they all need to take accountability.

Now that Tristan is free, he plans to take the Jolene and travel down the coast. The soul supernova broke the part of the sin eater curse that keeps him in Horseshoe Bay. He also realizes that even if he and Nancy could have loved one another, there'd always be someone else she loved more.

Bess tells Nancy that because of the damage done to her soul, this will be her last life. Ace's soul was also damaged, and this will be his last life. He went off to make peace with it but didn't tell anyone where he was going.

Nancy cleans out her room for the baby, even though Carson tells her she doesn't need to. She says she's always wanted to be a big sister and gives Carson a tiny beanie for the baby.

George tells everyone she got into law school.

Nick accepts an engineering position at Tom Swift's Atlanta incubator. He'll be developing and refining his own inventions, starting with the extractor device, and Jade has taken a PR position at the same hub.

Bess will be going on a global expedition to replenish the historical society's lost resources and knowledge. Addy is running for a town council seat and staying with the Underground Historical Society.

Nancy is taking on a new case. Her past life sent sin eaters across America. So, in this life, she will track them down and end the practice forever. But she's sure a mystery will eventually lead her back to Horseshoe Bay.

Ace had gone to North Carolina for Alice's memorial. It was the first step in forgiving himself. He plans to go pre-med and become a medical examiner. He's fifty percent sure that the death curse has been lifted since their souls were damaged, and Temperance never could have predicted this. He asks Nancy to help solve this mystery with him. She says yes, always, forever.

They kiss… and no one dies. So they keep kissing.

Later, at The Claw, before it is sold, the Drew Crew meets. In a special memorial area on the bar, they leave Grandma Fan's New England clam chowder recipe, a memento from the seder, and a fork "in case Jessie and Birdie have to do the fork thing." Ace leaves Nanette, the whistle he used so that Bess could find him in the mystical realm, in case anyone has to find their way home. Nancy leaves her name tag and says goodbye.

Ace carves all of their initials under the bar.

In a VoiceOver, Nancy says, "My Dad once told me it's possible to live a good life even without a soulmate. He was half right. It is. But now I know that we choose soulmates ourselves. Fate leaves that up to us. And like he also said, maybe you get more than one. I know that I have. I got four."

We watch the Drew Crew leave The Claw for the last time. Nick reminds the last person to turn off the lights. George and Nancy linger. George has tears in her eyes. Nancy tells her, "I got this." She turns off the lights as she's the last person to walk out the door.