Elizabeth Daly was born in New York City on October 15, 1878, the daughter of Joseph Francis Daly, a justice of the Supreme Court of New York County, and Emma Barker Daly. She was the niece of Augustin Daly, a famous playwright and producer of the 1890’s.
Daly was educated at Miss Baldwin’s School, Bryn Mawr College, and Columbia University. She received a bachelor of arts from Bryn Mawr in 1901 and a master of arts from Columbia in 1902. In 1902, she returned to Bryn Mawr College, where she was a reader in English and a tutor in French and English until 1906. She also coached and produced amateur plays and pageants.
At the age of sixteen, Daly had experimented with light verse and prose, some of which was published. Her primary interest during most of her life, however, was in amateur theatricals. From an early age, Daly had shown a fondness for games and puzzles, and this fondness resulted in a lifelong interest in detective fiction. She was particularly fond of the works of Wilkie Collins.
In the late 1930’s, Daly attempted to write detective stories. It was not until 1940, when she was sixty-two, however, that her first novel, Unexpected Night, was published. Fifteen more novels featuring the amateur sleuth Henry Gamadge and one novel of manners, The Street Has Changed (1941), followed during the next twelve years. Daly died in St. Francis Hospital, on Long Island, on September 2, 1967.