Gifted biologist Mary Clare Ryan's car has plunged into the Potomac River. Nicole Ryan suspects that her sister's death was no accident but when she tries to find out what research Mary was pursuing, Mary's colleagues are evasive, even hostile. Nicole is left with nothing except Mary's plane ticket to Los Angeles and a notebook she'd given Nicole ... in case anything happened to her.

Fleeing Georgetown's rain-slicked cobblestones and her own stagnant life as a professor, Nicole infiltrates the West Coast medical conference where her sister was slated to speak. She learns that just before Mary died she made a major scientific breakthrough, which she had gone to great lengths to conceal. Furthermore, those who stand to profit from her discovery have now targeted Nicole as the one most likely to have been in Mary's confidence. As she seeks out the truth about her sister's death, it becomes increasingly apparent that someone is stalking Nicole, tracking her movements in the sultry shadowy California night....