Episode 123 of "Sabrina, the teenage witch"
s06e04 Murder on the Halloween Express

Sabrina takes a holiday idea from Salem and brings her friends on the spooky Mystery Train for a Halloween adventure. There's just one problem: It's in the Other Realm. Sabrina soon learns that the mortals can leave only if she solves the puzzling mystery when she goes back into something out of a 1920 mystery movie. Halloween is a very important holiday to Sabrina so she wants to do something really exciting this year — and that does not include going to the dentists' school party.While trying to decide what to do for Halloween this year, Hilda notices a pamphlet for a murder mystery train. Zelda comments that they get that every year, but she doesn't want to go, she'd rather make taffy. Salem really wants to go on the train, but can't convince the aunts to take him. Sabrina spies the pamphlet for the train and decides it's a great idea for her friends. She announces their plans for fright night, but the group isn't all that enthusiastic about a murder mystery train — even Josh isn't very supportive. They go on the train anyway, which, from all appearances, is shabby and rundown. Sabrina heads to the bathroom, but when she returns, the group has been transformed into characters from the past, all involved in a murder mystery. Morgan is a countess, Roxie is her maid, Harvey is an international tennis star, Miles is a professor and Josh is a photographer who just also happens to have been murdered. Sabrina is the investigator and if she can't solve the crime, they will never get back home.The aunts discover that Sabrina has accidentally taken her friends on an Other Realm murder mystery train and go off to help her, bringing Salem along. When they finally catch up with the gang, they decide to use their wiles on the cute conductor who knows all the secrets, including who the murderer is... meanwhile Salem and Sabrina try to solve the crime. As it turns out, Sabrina's the murderer. Upset over Josh not supporting her Halloween idea, she "accidentally" hands Josh a piece of Zelda's taffy which isn't meant for mortals because it contains unicorn which is toxic. Now that the murder's solved, they all return to Boston and Josh apologizes for not supporting Sabrina even though she's supported him on everything from Prague to his new job.