 She went on to write several more young adult mysteries between 1965 and 1972.From 1972 to 1987, she wrote nine stand-alone suspense novels and mysteries, which had only modest success.Until the publication of mystery novels by Marcia Muller, Sara Paretsky, and Sue Grafton, publishers had little interest in mysteries written by contemporary American female writers; the success of these authors, however, opened the door for Hart's "Death on Demand" (1987), which became the first in a long-running series of the same nam.