The correct answer is Fran Farley.
The detective and his daughter adjourned to the kitchen and took out their matching police-issue notepads. "Let's eliminate the impossible," Harry started. "The ghost was played by a woman, so that eliminates our Scottish bear. Plus, he didn't know the facts written out in the note."
"Right," Amy agreed. "And the ghost must have had access to the parlor door, so that eliminates Rachel. She never had the chance to plant the note and knife."
"That leaves Millie and Fran. Both women knew Anne and both had motives."
"But only one came from a country closely associated with British customs and traditions."
"What's that got to do with anything?"
"Look at the note," Amy said. "The word 'favour' is spelled the British way, not the American way. Of course, there was another way to know it was Fran. The noise the knife made when it hit the door."
Harry checked his notepad carefully. "No one mentioned a noise."
"Exactly. Stabbing the door would have made a distinct noise, especially since it was stabbed more than once. The only explanation is that Fran stabbed the door ahead of time. Then, when she left the parlor, she produced the knife and note from her pockets and pretended she'd just taken them off the door."