Woody and Jordan investigate the murder of a military man who had just returned from a tour of duty in Iraq. Meanwhile, Macy has an argument with his daughter after she brings a boyfriend home; and Nigel uncovers new evidence in a decades-old kidnapping case.

Macy, Jordan, Woody and the rest of the crew are rocked by emotional and physical trauma when a commuter train carrying schoolchildren and their pregnant teacher is destroyed in a terrorist attack.