The Ghost and the Séance
by Hy Conrad
"All right," Harry said. "If we eliminate the ghost, then all the supernatural stuff was done by a human. Do you think it was more than one of them?"
Amy thought. "No. If you're plotting a crime, you need to trust your cohorts. From the evidence, they were all pretty much strangers to each other. The wife was new, the daughter was just arrived, and the medium was a first-time guest."
"So, we can pretty much eliminate the medium. He wouldn't have known where the medication was kept and he couldn't have impersonated the ghost."
"Oh, you can find ways to eliminate all of them, except one. Or you can do it another way. You can think about the sound."
"Exactly. The sound that no one heard."