The gang visits their friend Arlene Wilcox in Salem, Massachusetts for Halloween, only to encounter the spirit of her identical ancestor Milissa Wilcox, and must solve the case to prevent the townspeople from driving Arlene out of town.
This episode includes examples of the following:
- Artistic License – History: There are many, many inaccuracies. For starters, there were no burnings in Salem. Secondly, 1778 is far too late for any official witchcraft executions. The last person executed for witchcraft in the British Isles, for example, was executed in 1727. The practice was already dying by the time of the Salem Witch Trials in 1692.
- Catch Your Death of Cold: Because Scooby is dressed up as a witch for Halloween, the witch hunters mistake him for Arlene/Melissa and dunk him repeatedly in an effort to force him to confess. By the end of the episode, he's caught a cold from the dunking and Shaggy brings him chicken soup.
- Chekhov's Gun: The gang finds a marking in the family records for the Wilcoxes saying "Gemini", and they note it can't refer to an astrological sign because Arlene wasn't born in a Gemini month. "Gemini" is a constellation of twins; the marking foreshadows that Arlene has a secret twin sister.
- Disproportionate Retribution: Arlene Wilcox's sister goes through a lot of trouble against her, all for being left out of the family will. To the point that Arlene would have been sentenced as a witch. (Doubly so since Arlene didn’t even know the sister existed, thus she couldn’t have known about her absence from the will.)
- Karma Houdini: The townspeople who tried to get Arlene and Scooby to confess they are witches face no punishment other than quickly apologizing in the end.
- No Name Given: Arlene's twin sister never has her real name revealed.
- Separated at Birth: Arlene has a secret twin sister from whom she was separated early in life, and doesn't discover this until the reveal.
- Soup Is Medicine: Shaggy brings Scooby chicken soup when he catches a cold.
- Stranger Behind the Mask: The episode ends with the reveal that the witch is the previously unknown twin sister of the gang's friend.
- Undercover When Alone: At the beginning, a cemetery caretaker is working alone when he sees the Monster of the Week, screams, and runs away. It later turns out that he and the person in the monster costume are partners, raising the question of why he acted so terrified before there were any witnesses around.
- Witch Hunt: The ghost of Milissa Wilcox is plotting to instigate one and drive her descendent out of town, all so she — in her real identity of Arlene's twin sister — could claim Arlene's inheritance for herself.
