In this spin-off thirteen part story follows Cheryl Blossom, a high school mean girl who Riverdale High. Today's her 18th birthday and is having a birthday celebration and invites all of her close friends and family. Once the party ends, she is killed by a psychotic masked-killer who is out for revenge. Now, Cheryl must re-live her birthday until she figures out who is killing her. Anyone is a suspect and she cannot trust anyone not even her best friends.