Wikipedia: Three Doors to Death is a collection of Nero Wolfe mystery novellas by Rex Stout, published by the Viking Press in 1950 — itself collected in the omnibus volume Five of a Kind (Viking 1961). The book comprises three stories that first appeared in The American Magazine:

"Man Alive" (December 1947)
"Omit Flowers" (November 1948)
"Door to Death" (June 1949)

Amazon: "One by one they knock on the door of the incomparable Nero Wolfe, each with a case more perplexing than the one before. First comes the niece of a man who committed suicide by jumping naked into a geyser, only to return just in time to be murdered. Then it’s the strange case of the murder victim’s family covering up for the real killer, while a chef stews in jail. Finally a master horticulturist discovers the woman he wants to marry: dead and cooling in a hothouse. Three knocks on the door. Three cases of crime. Enter a world of mendacity, mixed motives, and masterful detection on West Thirty-fifth Street, where murder is always at home."