Green's The Step on the Stair enters the public domain.

House diagram from The Step on the Stair

The Tisch Library of Tufts University notes that one of the books that entered the public domain on 1 January 2019 is The Step on the Stair by Anna Katharine Green, which involves the murder of a wealthy man and a hidden will. "Admirable craftsmanship," deemed the World's News of Sydney, Australia.