The crime scene is as puzzling as it is brutal. Doctor Paul Latham and his wife, Brindel, are found dead in separate beds in their beautiful San Francisco home, each the victim of a gunshot wound to the head. There are no signs of forced entry, and despite the emptied safe it's clear this murder isn't random. For Detective Regan Pescoli, news of her sister's death brings grief mixed with guilt. She and Brindel weren't close, and Pescoli barely knows...

Targeted for murder after she takes custody of a mysterious notebook, Karen Whitlaw is protected by detective Marc Chastain, with whom she begins a passionate relationship while they seek to uncover the mystery behind the notebook's past.