The Thirteenth Chair is a 1937 American mystery film directed by George B. Seitz and starring Dame May Whitty, Lewis Stone, Madge Evans, and Elissa Landi.

[1] In Calcutta, India, Scotland Yard Inspector Marney (Lewis Stone) and local police Commissioner Grimshaw (Matthew Boulton)  discuss the murder of Leonard Lee as they approach the bungalow where he was stabbed in the back.

Wales proposes a séance, not to raise spirits, but to put psychological pressure on suspects.

They agree, and Grimshaw calls the Governor, Sir Roscoe Crosby (Holmes Herbert), to make arrangements.

At the Governor's residence, the participants gather: the Governor and his wife, Lady Crosby (Janet Beechery); their daughter, Helen Trent (Elissa Landi) and her husband, Major Lionel Trent (Ralph Forbes); their son, Dick Crosby, (Thomas Beck) and his mother's secretary, Nell O'Neill (Madge Evans), who is secretly engaged to Dick; Dr. Mason (Charles Trowbridge); Mary Eastwood (Heather Thatcher); Professor Feringeea (Lal Chand Mehra ); Mr. Stanby (Robert Coote) and his emotionally unstable sister, Miss Stanby (Elsa Buchanan); and Wales himself.

[2] After demonstrating some tricks (floating tables and disembodied knocking), she promises that there will be no trickery tonight.

The lights come on, revealing Wales, sitting in his chair, dead from a stab wound to the heart.

The medium is astonished to learn that this makes no difference to the Crosby family: They love Nell.

The lights flash on to show Wales' upraised arm pointing to the knife in the ceiling.