Dr. Dylan Reinhart and Det. Lizzie Needham are reassigned to a murder case in Central Park when their investigation into a chemical attack on the subway is taken over by an FBI team led by Dylan's estranged father, Roger. However, Dylan can't shake the feeling that the cases are related.

Dylan and Julian go undercover in a hospital when they suspect an "angel of death" is killing people with non-life-threatening ailments. Also, Lizzie asks Andy for his legal expertise when a personal trainer sues her for accidentally injuring him.