R.L. Stine's Mostly Ghostly: One Night in Doom House

To raise money for his girlfriend's school dance crew competition, magician Max conducts a public seance. Despite Nicky and Tara supplying genuine spectral thrills, all believe it to be Max' trickery, including Cammie (who, thereafter, breaks up with Max), when the ghost of a French maid butts in, leaving info in finding Nicky and Tara's missing parents. Since Nicky and Tara have complained about Max treating them more as pets than friends, Max turns to a famed ghost hunter (shooting a TV episode in town) for help, only to discover him a charlatan. Because of the shoot site, Phears the ghost demon ably takes possession of the pseudo ghost hunter to re-try releasing his evil ghost army upon the world. The discovery of a dark crystal in Max' house (which Max uses to try buying back Cammie's affections) becomes the linchpin to Phears' success, with fame, siblings, a rival suitor and an anxious choreographer only getting in the way.