Helen Reilly (nee Helen Kieran) was born and raised in New York City in a literary family. Her brother, James Kieran, was also a writer, and two of Reilly's daughters, Ursula Curtiss and Mary McMullen, are also writers. Reilly's early books were police procedurals based on her research into the New York Homicide squad. Reilly also used the pseudonym Kieran Abbey.