Dr. Allie Parsons finally has it all. Three years after narrowly escaping a murder attempt with her daughter and taking down notorious serial killer Toro, she's got a residency at the morgue and is set to marry hotshot attorney Duncan Maxwell. Then a mysterious note arrives, seemingly written by a child and warning of Toro's return. With the threat of more impending deaths, Allie is once again pulled into the past.
While searching for the child's identity and location, Allie discovers a string of murder victims across the country with possible Toro connections. Her fiancé encourages her to investigate, and she's aided by an old friend, Andrew Wong. However, the deeper into the case Allie goes, the more her stable life and career start to unravel.
When Allie quits her residency to continue the search, Duncan tries convincing her to accept a job offer from his employer, Minos, which specializes in genetics and has lucrative resources she can use. But Allie can't be tied down, especially when she finds the victims share a common trait. Toro-or a copycat-is leading her on a chase with the murders, and Allie is determined to solve them before she's next.