Season 6, Episode 4 of Riverdale kicks off with a sequence exploring the strange love story of Abigail (Madelaine Petsch) and a teacher named Thomasina Topaz (Vanessa Morgan). Despite their initial disagreements, the two end up falling for each other. But a warlock ruins everything. How does Nana Rose (Barbara Wallace) come into the story? Hold tight.

A warlock named Finn forces Abigail to get married. Along the way, he murders Thomasina. Ultimately, Abigail tries to kill him so as to get rid of him once and for all, but Finn wins once again.

In essence, he puts a curse on her, forcing her to spend the rest of her life in solitude, unloved. An immortal woman, Abigail later on transforms into a free time potion-maker named Poppy (Madelaine Petsch) and eventually, Cheryl.

Back in the present, Cheryl is spending an increasing amount of time looking after Nana Rose. She reaches out to an old friend from softball, Sabrina Spellman (Kiernan Shipka), who helps her prepare a transference spell — the exact same type she relied on in Season 4 of Chilling Adventures of Sabrina.

Cheryl's spirit takes up residence inside Nana Rose's body, while Nana Rose's spirit goes into Cheryl. Nana Rose's body dies with Cheryl's soul in it. The main idea behind the operation is to put Abigail's soul at rest and to do so, they need to kill the fleshy vessel inside which it is.

To recap: Cheryl was the newest reincarnation of Abigail, the poor woman still pining to have a go at a relationship with her long-lost love, Thomasina (to clarify: yes, Thomasina died at the hands of Abigail's scheming warlock of a husband), whose problems were solved once she died.

In essence, Abigail's soul went straight to the Sweet Hereafter — that's another CAOS reference for you — where it got the chance to finally hang out with Thomasina's soul.