The synopsis for the fourth episode of Riverdale Season 6 teases Sabrina Spellman's arrival from Greendale in the upcoming crossover.

According to the synopsis, the episode will see Cheryl and Nana Rose reminiscing on tragic family stories involving the Blossom women. Elsewhere, the Blossoms will no longer be the only witches in Riverdale. Sabrina Spellman will finally arrive in town after Cheryl summons her with the help of Bailey's Comet.

Related: Riverdale Welcomes Sabrina Spellman with a Supernatural Season Trailer

Writer George Gladir and artist Dan DeCarlo created Sabrina Spellman, who first appeared in a comic series with Archie's Mad House #22. The character has appeared in other mediums, most notably Sabrina The Teenage Witch and Netflix's Chilling Adventures of Sabrina series. The latter follows a teenage Sabrina as she balances her mortal life with her supernatural side. The series finale of Chilling Adventures of Sabrina culminated with Part 4, released in December 2020.

Chilling Adventures of Sabrina and Riverdale showrunner Roberto Aguirre-Sacasa confirmed that the ending of CAOS is canon in the Riverdale universe. The writer told EW, "We definitely refer to the end of Chilling Adventures, and we own how that ended and how she's back."

Related: Riverdale Fans Can't Believe [SPOILER] Is Really Dead

Riverdale Season 6 kicked off Nov. 16 with the first of five episodes in the "Rivervale" event, The CW's take on its superhero crossovers like The Flash's "Armageddon" and "Crisis on Infinite Earths." "Rivervale" acts as an alternate universe of sorts, having entered the warped reality presumably after the events of the Season 5 finale. Before Hiram left town, he planted a bomb underneath Archie's bed and waited until he was on his way out of the town to detonate it. Aguirre-Sacasa describes the episodes as "firmly in the horror genre" and confirmed they have their own arc.

The full synopsis for "Chapter Ninety-Nine: The Witching Hour(s)" reads as follows:

SABRINA SPELLMAN (GUEST STAR KIERNAN SHIPKA) COMES TO RIVERVALE — As Bailey’s Comet passes over Rivervale, Cheryl (Madelaine Petsch) and Nana Rose (guest star Barbara Wallace) revisit the tragic stories of the Blossom women through the years. Meanwhile, the once-in-a-lifetime celestial event prompts Cheryl to summon a familiar face to Rivervale – Sabrina Spellman (guest star Kiernan Shipka). Lili Reinhart, Camila Mendes, Cole Sprouse, Madelaine Petsch, Mädchen Amick, Casey Cott, Vanessa Morgan, Charles Melton, Erinn Westbrook and Drew Ray Tanner also star. James DeWille directed the episode written by Arabella Anderson

Riverdale Season 6, Episode 4, "Chapter Ninety-Nine: The Witching Hour(s)" will air Dec. 7 on The CW.

Keep Reading: Riverdale: Sabrina's Crossover Can Adapt Archie Comics' Most Horrific Story

Source: The CW, EW