Helen McCloy was born in New York City. Her mother was the writer Helen Worrell McCloy and father, William McCloy, was the longtime managing editor of the New York Evening Sun. Having read Sherlock Holmes as a young girl, McCloy retained an interest in mysteries and began to write them in the 1930s. Her first novel, Dance of Death, was published in 1933 and was followed by several other crime publications in the 1940s.
The most famous of McCloy’s characters was Dr Basil Willing, who subsequently appeared in twelve of her novels and several short stories. McCloy often used the theme of doppelgänger, but at the end of each story she showed a psychological or realistic explanation for the seemingly supernatural events. What can be considered as one of McCLoy’s masterpieces is the eighth Basil Willing novel, THROUGH A GLASS DARKLY (1950), a supernatural puzzle in the tradition of Dickson Carr.
In 1946 McCloy married Davis Dresser, who had gained fame with his Mike Shayne novels, written under the pseudonym Brett Halliday. She founded with Dressler the Torquil Publishing Company and a literary agency (Halliday and McCloy). Their marriage ended in 1961. In the 1950s and 1960s McCloy was a co-author of review column for Connecticut newspapers and in 1950 she became the first woman to serve as president of Mystery Writers of America. In 1953 she received an Edgar from the same organization for her critics.