Detective Abigail Boone has been missing for four days when she is finally found. Suffering retrograde amnesia, she is a stranger to her despairing husband and bewildered son. Hopelessly lost in her own life, with no leads on her abduction, Boone's only instinct is to revisit the case she was investigating when she vanished: the baffling disappearance of a young woman, Sarah Still.

Defying her family and the police, Boone obsessively follows a deadly trail to uncover the shocking truth. But even if she finds Sarah, will Boone ever be the same again?