They do it with Mirrors

Miss Marple senses danger when she visits a friend living in a Victorian mansion which doubles as a rehabilitation for delinquents. Her fears are confirmed when a youth fires a revolver at the administrator, Lewis Serrocold. Neither is injured. But a mysterious visitor, Mr Gulbrandsen, is less fortunate - shot dead simultaneously in another part of the building. Pure coincidence? Miss Marple thinks not, and vows to discover the real reason for Mr Gulbrandsen's visit. Agatha Christie does it all with suspense in this intricately plotted mystery.