Characters of the Book
- Philo Vance
- John F.-X. Markham
- District Attorney of New York County.
- Ernest Heath
- Sergeant of the Homicide Bureau.
- Professor Bertrand Dillard
- A famous physicist.
- Belle Dillard
- His niece.
- Sigurd Arnesson
- His adopted son: an associate professor of mathematics.
- Pyne
- The Dillard butler.
- Beedle
- The Dillard cook.
- Adolph Drukker
- Scientist and author.
- Mrs. Otto Drukker
- His mother.
- Grete Menzel
- The Drukker cook.
- John Pardee
- Mathematician and chess expert: inventor of the Pardee gambit.
- J. C. Robin
- Sportsman and champion archer.
- Raymond Sperling
- Civil Engineer.
- John E. Sprigg
- Senior at Columbia University.
- Dr. Whitney Barstead
- An eminent neurologist.
- Quinan
- Police Reporter of the World.
- Madeleine Moffat
- Chief Inspector O’Brien
- Of the Police Department of New York City.
- William M. Moran
- Commanding Officer of the Detective Bureau.
- Captain Pitts
- Of the Homicide Bureau.
- Guilfoyle
- Detective of the Homicide Bureau.
- Snitkin
- Detective of the Homicide Bureau.
- Hennessey
- Detective of the Homicide Bureau.
- Emery
- Detective of the Homicide Bureau.
- Burke
- Detective of the Homicide Bureau.
- Captain Dubois
- Finger-print expert.
- Dr. Emanuel Doremus
- Medical Examiner.
- Swacker
- Secretary to the District Attorney.
- Currie
- Vance’s valet.