Charlotte Armstrong was born on May 2, 1905, in Vulcan, Michigan, to Frank Hall Armstrong and Clara Pascoe Armstrong. Her mother was Cornish. Her father was of Yankee stock, an engineer at an iron mine. In her autobiographical novel The Trouble in Thor (1953), the character based on her father, the engineer Henry Duncane, is a kind of amateur detective. In exploring a problem in the mine, Duncanenever seemed to fumble. If he did not at once perceive the source of trouble and its remedy, he at once began to look for it. And Duncane’s groping was so full of purpose; he hunted for cause with such order and clarity, that he was totally reassuring.
Armstrong attended high school in her hometown and went on to the University of Wisconsin, completing her bachelor of arts degree at Barnard College in 1925. She became a career woman in New York City. Her first job was selling classified advertisements over the telephone at The New York Times. She also worked as a fashion reporter and a secretary in an accounting firm. On January 21, 1928, she married Jack Lewi, an advertising man.
Armstrong retired to private life and eventually to the rearing of three children, managing to write in her spare moments. She began with poems and then moved to plays. Her tragedy, The Happiest Days (pr. 1939), and her comedy, Ring Around Elizabeth (pr. 1941), were both produced on Broadway. Neither did well at the box office, but while the second was in rehearsal, she sold her first mystery, Lay on, Mac Duff! (1942).
This and her next two novels were of the amateur investigator type and were moderately well received, but she seemed to find her métier with The Unsuspected (1946), which was a work of suspense. This work was filmed in 1947, and she relocated to Hollywood with her family from New Rochelle, New York, to supervise the screenplay.
The family remained in California, living in Glendale, and Armstrong continued writing. Her novel Mischief (1950) was adapted for film as Don’t Bother to Knock (1952). In 1957, she received the Mystery Writers of America’s Edgar Allan Poe Award for her novel A Dram of Poison (1956). Armstrong died after an illness on July 18, 1969, at Memorial Hospital in Glendale, California.