An illicit arms dealer reveals a deal involving another dealer; McGee and Ziva tail a key player, who dies. Ducky impersonates the dead man and meets the Frog, whom Jen has long pursued; much good results, but the gang do not get the Frog.

A couple find the body of a Navy petty officer in an abandoned restaurant in Georgetown; the Metro PD calls and helps the NCIS; Gibbs and company investigate. Messages leave clues leading to an exclusive nightclub. The gang figure it out.

Jen meets with an informant about the Frog, but someone kills the witness; Gibbs and company investigate. Jen obsesses about catching the Frog. Abby produces many answers; although the gang persist, they find a surprise but no Frog.

While Jen attends a conference in Paris, Gibbs serves as the acting director. When a taxicab delivers a fare to the NCIS headquarters, the passenger, a Yemeni, is DoA; the gang investigate. Jen diverts to Moscow, and many answers emerge.

Jen returns from Paris; at home she finds a curious sight. All NCIS agents in Washington must take polygraph tests; Gibbs and the gang look into that. Tony and Jeanne deal with an injured pedestrian; Jeanne introduces Tony to her father.

Tony meets Jeanne's father; Tony excuses himself to move his Mustang, which explodes while the gang watch; Ducky says that the victim is not Tony. The Frog meets Jen, but she lets him leave; Gibbs and others pursue him but arrive too late.

Fornell and his Hoovers arrive in the squad bay; he tells that the Gibbs team is under investigation for the murder of the Frog. However, the Gibbs gang investigates the FBI, and they put the pieces together and explain them to the suits.

In Los Angeles, Jenny, with Tony and Ziva as a protective detail, attends the funeral for a retired long-time special agent, who supposedly died of a heart attack; Jenny hears a name, sees a man, makes pictures, and summons Mike Franks from Mexico; she tells him that she's the next person to die. Jen and Franks visit the home of the dead man; there they meet his girlfriend, whom they send to Nevada, but who winds up dead in Santa Monica. Jen and Franks check out an insurance policy at a diner in a desert, and she refuses help from Tony and Ziva; Franks steps outside in the back, then four men enter the diner, and gunshots ring out; Tony and Ziva find a mess inside. [To be continued.]

Dr. Cyril Taft feels the rush of an NCIS case when he's assigned to operate on Gibbs' suspect and discovers key evidence.