Late in “The Magician’s Nephew,” episode 64 (2008) of the U.K.’s long-running Midsomer Murders series, DCI Tom Barnaby (John Nettles) laments to his wife Joyce (Jane Wymark), who is busily planning an American-style Halloween party, “You know, in my day, Joyce, Halloween hardly existed. What’s it all for? Selling a load of flaming tosh!” Joyce suggests Tom should lighten up, but he’s finding it hard just then, being in the middle of a case involving real-life witches. “I’ve got two very unpleasant murders here,” he muses, “and I don’t know why, but they both have to do with people who actually believe in all this magic, this voodoo.” Joyce, as is her wont, then makes a very interesting offhand remark. “Well, that’s adults. Children have more sense. They only pretend to believe in Halloween, for the fun.” A key feature of the story, belief , misguided, sincere, and unsuspended, is depicted in scenes of solemn occult rites, church services, and an elaborate children’s magi...