Payton Shields had known from the time she was a child that she wanted to be a doctor. Now she's in her first year or residency at a major Boston children's hospital. She's made it to the top through relentless drive, stellar academic credentials, and a mountain of debt to Harvard Medical School. She's working impossibly long hours but she has the life she wants.

Then, late one night, driving home through a heavy snowstorm, she sees a car coming straight toward her, driving her off the road and into a frozen pond. Rescue comes in the form of a man who pulls her from the wreckage and walks away. Yet nobody believes her story, that the "accident" was no accident.

This is the first in a series of strange, escalating events that take Payton deeper into danger from a faceless enemy who seems to know her every move. And she has to turn her considerable determination into catching a killer before he catches her.