Retired CIA agent Dr Dylan Reinhart is asked to help a detective who is trying to catch a serial killer, one using Dylan's first novel as a guidebook.

Dylan helps to investigate the murder of a venture capitalist, having returned to teaching after assisting the NYPD catch a serial killer.

Dylan and Lizzie take a look at potential suspects after a young man is murdered soon after leaving his family's religious community. Lizzie's younger sister makes an unexpected visit.

After the FBI takes over their case of a chemical attack on the subway, Dylan and Lizzie are reassigned to investigate a Central Park murder.

Lizzie and Dylan race to find the dangerous killer who murdered an innocent Jane Doe. They realise that the victim was killed by mistake and must discover the killer's motive.

Dylan and Julian go undercover at a hospital to catch a dangerous killer who is targeting innocent patients. The killer is known as the `Angel Of Death' as he murders people with non-life-threatening ailments.