Margaret Millar (née Sturm) was born in Ontario in 1915, and married Kenneth Millar—better known as Ross Macdonald—in 1938. The Invisible Worm, set in Toronto, was published 1941, preceding her husband's first novel by three years.

Over the next 45 years she published over two dozen books, won the Mystery Writers of America Edgar Allan Poe award in 1956, and the Grand Master award in 1983. In the mid-40's, the Millars relocated to Santa Barbara, where they became active in the conservation movement. She was named a Woman of the Year by the Los Angeles Times in 1965. Millar died on March 26, 1994.