The Dr. Fell mystery The Hollow Man (1935), usually considered Carr's masterpiece, features crimes that are variations on both of these scenarios and that has a notable discourse by Dr. Fell on the nature of impossible crimes.
The Dr. Fell mystery The Hollow Man (1935), usually considered Carr's masterpiece, features two locked room mysteries, that are impossible on first appearances. The book includes a notable discourse by Dr. Fell on the nature of impossible crimes.