A sailor in Rota, Spain dies of unexpected heart failure. Abby discovers that he was actually killed by cyanide poisoning in the cookies he received as part of a care package from a stranger back in the United States.
The team contacts the man, a retired veteran named John Ross, who regularly sends care packages. Ross has a checkered past after being held captive for five years, but they don't believe he's responsible.
The situation grows more tense when a shock jock points the finger at Ross, citing information that he shouldn't have access to.
Hunting the information back to its source, the team discovers that the murder victim's own brother and wife were responsible; the wife wanted out of the marriage and had hooked up with her brother-in-law.
They set up Ross to take the fall for their crimes, but they are caught and arrested and the whole story quickly comes out.
Meanwhile, Jack Sloane bonds with Ross over share past experiences, specifically being in enemy hands. Sloane discovers that Ross actually has a living daughter, who doesn't know he exists.
She encourages him to connect with her and share the extensive family heritage he knows. As Ross does so, Sloane is still not quite able to come to terms with her own guilt over the death of her comrades years before.