Mac discovers the reason for a false positive result of a drug test for an angry woman enlisted Marine, and Harm and Bud represent a senior chief petty officer who is HIV-positive, and whose privacy has become compromised.

A Marine dies in an ambush in Iraq; his sister is a classmate of Mattie; Harm and Mattie help the mother and the sister of the Marine. Bud investigates the failure of the body armor. Harm and Mattie continue to understand each other better.