Born Gunard Hjerstedt in Chicago in 1903, Day Keene became an actor in repertory theater in the early 1920's. When his actor friends decided to try film, he instead turned to writing, and during the 1930's was a principal writer for the Little Orphan Annie radio show, as well as contributing to the pulps. After he moved to the west coast of Florida, he began writing paperback originals in the late 1940's, mostly fast-paced crime stories. By the 1960's, he had abandoned mysteries for mainstream novels. He died in North Hollywood in 1969.