They Do it with Mirrors
by Agatha Christie
As the story opens, Jane Marple is paying a visit to her old friend Ruth Van Rydock. The two, along with Ruth's sister Carrie Louise, were all friends together at the same school in Italy when they were young women. She can't explain any real reason for these worries, but she fears that Carrie Louise may be in danger of some kind. Ruth asks Miss Marple to visit her and find out what is going on.