Johnston was born in
Pittsburgh, Pennsylvania, the daughter of Isabel McElheny and John Parry Johnson. Her work is often confused with that of her mother's, as her mother—a journalist—also wrote a few scenarios and was credited under her married name,
Isabel M. Johnston. Her older sister,
Agnes Christine, was a screenwriter in Hollywood. As a teenager she began reading scripts for
Vitagraph, and after graduating from
Vassar in 1919, she returned to the film industry to write a string of films between 1920 and 1923. After working in Hollywood, she moved back to London for a few years to work with producers over there. She'd also write short stories for several decades. Johnston, who never married, died in New York in 1981. == Selected filmography ==