Miss Marple - Series 3 - They Do It with Mirrors

At the insistence of Ruth Van Rydock, an old schoolfriend who is convinced that there is something wrong, Miss Marple agrees to visit 'Stonygates', the country house of Ruth's sister. Edgar Lawson and Lewis Serrocold are heard arguing in the next room whilst everyone else is gathered in the sitting room after dinner. A shot is heard from within the locked room but when the door is opened, Edgar is found sobbing and the revolver is on the floor with Lewis unharmed. However, Christian, Carrie-Louise's stepson by her first marriage, is found dead.