'Riverdale': Shannen Doherty Mystery Role Revealed in Season 4 Premiere

Shannen Doherty joined the cast of Riverdale for a special tribute episode to her old friend Luke Perry. The actress' role on the show had been kept a mystery until the show aired, revealing her key role in the sudden passing of Perry's character, Fred Andrews. Doherty's character debuted in a heartbreaking scene alongside Archie (KJ Apa), Veronica (Camila Mendes), Betty (Lili Reinhart) and Jughead (Cole Sprouse).

Spoilers ahead for Riverdale Season 4 Premiere: "In Memoriam"

Doherty was introduced as Archie and the crew took some time to pick up Fred's (Perry) car from the side of the road where he was the unfortunate victim of a hit-and-run.

After finding out his father's body wouldn't be transported back to Riverdale until the day after the Fourth of July holiday, Archie decides to travel with his friends to the neighboring town where it happened to take the body back home himself. The mortician gives them a hard time and initially refuses to release the body to teenagers, but Mary (Molly Ringwald) convinces him to do it over the phone.

With a few hours before the body is ready for transport, the crew takes the opportunity to retrieve Fred's truck from the site of the accident. They drive to the place and find Fred's truck sitting on the road. Archie goes in and finds his things as he left them, including a photo of Archie and Mary in the glove compartment.

He is surprised when a car parks behind him and a woman (Doherty) steps out of the driver's seat holding flowers. Archie steps out of the car and asks her if he can help her, and she responds with a nervous no.

"I'm just paying my respects," she says. Archie asks how she knows what happened there and she asks him if he is Archie.

She reveals she is the person who Fred pulled over to help after her tire blew on the road. She shares how Fred talked about Archie the whole time they were working on the tire, wondering how a guy like him was blessed with such a caring son. She then says they were working on the tire when the other car came out of nowhere. She breaks down as she tells Archie that Fred pushed her out of the car's way, saving her life over his own.

"If he hadn't done what he did there's no way I'd be here right now, I know that," she says. "I'm so sorry, there's nothing I can do to ever repay him. But I would like to say a prayer for him." All five of them join hands to say a prayer for the late Fred Andrews.

Doherty previously spoke out about making an appearance on the show to help honor Perry's legacy.

"I am deeply honored to pay tribute to Luke on Riverdale. The care in which this show takes in honoring his memory is beautiful. He is missed. Today. Tomorrow. Forever," Doherty wrote on Instagram in July.

Riverdale airs Wednesdays at 8 p.m. ET on The CW.