A woman is found dead in an elevator, but her murder is just the beginning; as Barbara retraces the chain of evidence, she uncovers a domino effect of violence that leaves a trail of bodies across the Bronx.

In 2012, a tight-knit Las Vegas neighborhood is shattered by the murder of a mother and daughter in their home. Investigators must analyze a crime scene soaked in rage to help stop a killer before they strike again.