BELIEF IN THE OCCULT also figures in quite a different mystery, A Medium for Murder (McKay-Washburn, $6.95), by Mignon Warner. When the self-possessed Mrs. Charles is identified as a suspect in a sensational murder at a seaside resort ten years before, the English villagers remember their own unsolved homicide a few years later. Mrs. Charles, a clairvoyantle who plays the Tarot cards, must clear herself of suspicion in both. The plot is well-turned, with that last little twist of suspense, and Warner does well by her characters.

The old ghosts are very real in The Witch Hill Murder (St. Martin's, $7.95). Pauline Glen Winslow is a graceful writer and can be delightfully amusing if you allow her to proceed leisurely with her tale, taking time for wry observations on her characters and their doings.

British mystery writers always have had great fun with semi-dotty cuts (Ngaio Marsh, for one). For Winslow, it's the adolescent followers of Siderea, who bear no small resemblance to the Moonies in their zeal for self-perfection and fervor for recruitment. There are hundreds of Siderean suspects with iron-clad alibis when Richard Brewster is murdered in the English hamlet of Daines Barington. Scotland Yard Superintendent Merle Capricon, the magician's son who suffered claustrophobia in sealed trunks and became a policeman instead, has more than a professional interest in the case. His old friend and flame, Rose Lavender, was engaged to Brewster, who even Capricorn must admit was a fine fellow. Capricorn must use some old magician tricks to escape a death trap and a psychological ghost from the past.