Jughead eats at Pop's, which is decked out for Christmas. Archie and Fred bring a Christmas tree into Pop's.

Archie and Jughead catch up, and reveal that they've both broken up with their girlfriends. They agree to meet at Kevin's Secret Santa party.

Betty is woken up in the middle of the night by Polly. She leads her downstairs, where she finds her family -- as well as the Black Hood, dressed like Santa. He climbs through the room, ready to kill her, when she wakes up from her dream.

Penelope, Cheryl, and Grandma Blossom meet in the kitchen. Penelope tells Cheryl they won't have enough money to celebrate Christmas.

Fred gets his bills from the hospital, and Archie is upset to find that they cost $86,000.

Veronica and Betty prepare for Kevin's Secret Santa. They talk about their breakups.

Jughead talks to FP about his problem with Penny Peabody. FP invites some Serpents inside who are carrying suspicious packages.

The gang opens their Secret Santa gifts. Veronica gets a gift card for a couple's massage. Betty gets a gift from Archie; an old book that she and Archie used to love as kids.

Moose and Midge return from the hospital.

Archie tells Betty that seeing Moose reminds him of the Black Hood. The pair both feel anxiety about the Black Hood still being out there. Betty notices that there's a new janitor at Riverdale High, and that Mr. Svenson has gone missing.

ACT II

Archie and Betty ask the school receptionist about Mr. Svenson's absence. She explains that he's home sick and depressed since he's alone for the holidays.

Jughead gives Betty a Christmas gift. He apologizes for breaking them up, but Betty stands by the choices she made. She gives him a Christmas present.

Veronica gives Archie a Christmas gift. He opens it and finds a personalized watch. She says that she still wants them to be close, even if they're not together. Archie tells her about Fred's hospital bills, and she offers to help.

Jughead finds the Serpents at the White Wyrm, preparing gifts for local charities. FP gets annoyed that Jughead is there, and doesn't let him do Serpent things.

Betty calls Archie, suggesting that they go check on Mr. Svenson. Cheryl attempts to buy a tree from Archie, but he leaves.

Archie and Betty visit the Svenson house.

Jughead gets a visit from FP's parole officer.

During dinner, Veronica tells her parents about Fred's financial situation. Hiram grows upset and leaves.

Cheryl decorates a Christmas tree in the Blossom house. Penelope gets upset, and Cheryl suggests that Penelope try to find a job to support them.

Betty comes home to find Alice baking cookies. She reveals that Betty got a present from her Secret Santa. She opens it to find a human finger.

Act III

Archie and Betty read the note, which reveals that the finger belongs to Mr. Svenson. Betty gets a phone call of Mr. Svenson being tortured by the Black Hood. He tells them to find the "cardinal sin" of Riverdale in order for Svenson to survive. They remember that Svenson used to live at the Sisters of Quiet Mercy, and go to get information from them.

Veronica sneaks around Hiram's office. She finds the documents revealing that Hiram bought Pop's.

FP comes home to find Jughead. Jughead reveals that the parole officer stopped by, and is curious about the suspicious bags. As FP reveals, the bags are filled with Christmas presents for their family. They debate about how to handle the Penny Peabody situation.

Veronica uses her mom's credit card to settle Fred's medical bills.

Jughead tells Toni and the other teenage Serpents about Penny's hold on the Serpents. He suggests that they kill her, as a way to save themselves from being roped into her drug trade. Toni, Sweet Pea, and Fangs accept.

Betty and Archie visit Sisters of Quiet Mercy. They're vague on the details, but Betty threatens to expose the place's injustices if they don't tell her more. The Sister reveals that Svenson identified the man who killed his family, and he was executed by the town because of it.

But as Svenson revealed when he lived at the convent, he probably sentenced the wrong man. She also reveals that the people who committed the murder happened to visit Svenson -- including Nana Blossom.

Act IV

Jughead and the Serpents visit Penny. They kidnap her.

Veronica's parents come home, and reveal that the bank called them about the credit card charge for Fred's bills. Veronica confronts them about Pop's. Hermione and Hiram decide to tell Veronica the truth.

Jughead and the Serpents drop Penny off in Greendale, and tell her to stop dealing with the Southside. Penny says that Jughead can't hurt her since she's also a Serpent. But Jughead pulls out a knife and slices off her tattoo.

Betty and Archie visit the Blossom household. They ask Nana Rose about the Svenson case, and she reveals that she wasn't allowed to be part of the killing. She reveals that they didn't hang him; they buried him alive. She won't reveal where, but she reveals that Betty's grandfather was one of the men involved.

Betty freaks out about her grandfather possibly being involved with the murder, and wonders if that's why the Black Hood is after her. Archie promises that they will stop the Black Hood, and the pair kiss.

Act 5

Veronica is shocked by her family's revelations. She offers to still be involved with Lodge Industries, as long as she isn't doing anything illegal. They agree.

Jughead sits FP down for dinner. He reveals that they drove Penny out of town, but FP swears that Penny will find a way back. Jughead reveals that he's proud to be a Serpent, and that FP's rules won't change that.

Betty and Archie look through her old family photo album. They find the photo of her grandfather and his friends at Pickens Park -- next to a freshly marked grave. They decide to call Sheriff Keller and leave.

Betty and Archie find Svenson buried alive in a coffin. They dig him out, and find the coffin empty. The Black Hood sneaks up next to them, and asks Archie to get in the coffin. Betty reluctantly agrees.

The Black Hood holds Betty at gunpoint as she is forced to bury him alive. She pleads with the Black Hood, saying that she can unmask Svenson's sin if that's what he wants. The Black Hood gets distracted by sirens in the distance, and Betty hits him over the head with a shovel.

Betty and Archie chase the Black Hood to the bridge. The Black Hood attempts to jump, but he is shot in the process by Sheriff Keller.

Keller comes up to the body, and unmasks him. It's Mr. Svenson -- with his own finger cut off and everything.

Act VI

Archie and Betty tell Veronica and Jughead about Svenson. They try to determine why Svenson did it. They realize that Svenson could have seen all of the "sins" in Riverdale by being the janitor.

Everyone celebrates Christmas.

Cheryl finds her mom hooking up with someone dressed as Santa.

Veronica finds a gift under the tree from Archie.

Jughead opens his present from Betty; it's a really nice typewriter.

Betty opens her present -- a book from Jughead.

Veronica opens Archie's present -- a locket with his picture inside.

Archie and Fred call Mary, but Archie gets a text from Veronica asking him to meet outside. They stand under mistletoe and kiss. Veronica tells Archie that she loves him back, and the pair continue to kiss.

Someone snaps photos of Veronica and Archie kissing from the bushes.

Betty opens a box to find all of the Black Hood's ciphers and headlines. She burns them in the fireplace. She also begins to burn her Black Hood, before grabbing it and holding it in her hands. As Jughead explains in his narration, this isn't over just yet.