Tony and Ziva fly to Paris, pick up a witness (a whistle-blower) for a federal criminal trial, and escort her to Washington, DC. Meanwhile a maid finds the body of a Marine special-ops sergeant in the bathtub in his apartment in Washington; Gibbs and company investigate; McGee finds a safe, so he and Gibbs open it; they find a connection to the whistle-blower. Gibbs and McGee have an interesting chat with a madam, and they meet the fiancé of the witness. Tony and Ziva find a problem with the air marshal aboard their homebound flight, then the witness runs into trouble; Tony and Ziva encounter an uncooperative flight attendant, but they work things out, with the expert help of Gibbs, McGee, Ducky, and Abby. Gibbs gets a sore shoulder.