While investigating an overturned van in Washington, DC, the Metro PD finds cargo marked as the property of the USMC; Gibbs and company take over; the gang find crates of body armor, which Abby determines to be faulty and fatal. Ellie, the new probie, discovers what caused the wreck, then Tony interviews the two boys who did it; they give a clue, which points to the missing driver; Gibbs and the three musketeers find his body at his pad. Abby gives a hard time to an official of the manufacturer of the faulty armor; Gibbs and McGee speak with a discharged Marine with experience with faulty armor; a group of concerned mothers shows up, and they start asking questions. Tony and Ellie interrupt a rendezvous, then Gibbs and Ellie get some answers. McGeek asks a seminal question, which leads to two more meetings, one of which results in a confrontation and a demonstration of the faulty armor. McGee introduces someone to Delilah, who gives McGee a dare.