The John Dickson Carr novel also known as The Three Coffins is The Hollow Man.
Published in 1935, The Hollow Man is a classic locked-room mystery featuring Carr’s recurring investigator Dr. Gideon Fell. Its plot presents apparently impossible crimes, including a shooting in a room that seems sealed and a murder in snow where the only visible footprints belong to the victim.
The title The Three Coffins was used for the American edition, while The Hollow Man was the original British title. The novel’s central intellectual set piece is the “locked room lecture,” in which Dr. Fell discusses the practical methods a murderer might use to create the illusion of an impossible crime. The chapter has become one of the most frequently discussed passages in detective fiction.
Readers sometimes confuse this book with Carr’s other mysteries, including The Plague Court Murders and The Judas Window. The Hollow Man is especially notable because a 1981 panel of mystery writers and reviewers selected it as the best locked-room mystery of all time.