Mrs. Bradley Mysteries

The Mrs. Bradley Mysteries was a 1998-2000 British mystery series starring Diana Rigg as expert criminologist Beatrice Adela Bradley. The series was based on a series of detective novels written by English author Gladys Mitchell.

Death at the Opera (Season 1, Episode 2)
Mrs. Bradley visits Hadleigh Heights, her alma mater. She has been invited to give a speech following a student production of "The Mikado," but during the performance, one student fails to appear on stage. The missing student is soon discovered dead backstage. Although initially chalked up to a tragic sudden death caused by a heart condition, Mrs. Bradley's investigation gradually uncovers a more sinister murder plot. Using a pendant, she hypnotizes Plum Fisher (Carli Norris), a student at the school. Under hypnosis, Plum admits that she knew about the student's heart condition and planted spiders in her dressing room to scare her to death, to keep her from telling anyone about Plum's kleptomania.