The Thirteenth Chair (1919)

Mrs Philip Mason commits suicide after she has an affair with Stephen Lee a disreputable stockbroker and sells her husbands securities so that Lee can buy stocks When Lee goes bankrupt he blackmails Helen Trent by threatening to reveal silly love letters she wrote to him before she married Her brother Willy Grosby and his fiancée Helen ONeil who lives with the Grosbys go to retrieve the letters While Willy waits outside Lee is knifed to death as he attacks Helen Lees friend Edward Wales attempts to pin the murder on Helen by having Madame LaFarge a clairvoyant conduct a séance In the darkened room Wales through whom Lees spirit supposedly speaks is about to name Helen as the murderer but Wales who sits in the thirteenth chair is himself murdered After Helen confesses to Inspector Donohue that Madame LaFarge is her mother LaFarge while conducting another séance tricks Philip Mason into confessing to the murders