When Marine Corporal Flegman is found shot to death, NCIS is called in to investigate and they discover he had several missed calls from a hotel room just prior to his murder. To the team's surprise, they find Diane Sterling and FBI Special Agent Fornell in the hotel room engaging in a romantic rendezvous. Diane had been attempting to call her boyfriend Eddie to break up with him, but Flegman had possession of Eddie's cellphone. After they find Eddie's car, Gibbs agrees to Bishop's plan of organizing a stakeout to track his activity. They follow him to a storage unit full of concealed cash and apprehend him there. While being interrogated, Eddie explains that he is an undercover agent working on a money-laundering case. He had traced the money to a bank-robbery gang and infiltrated their group. Flegman was their getaway driver and the head of the gang, Patrick, ordered a hit on him for skimming from the top. With Eddie's cover blown, Patrick kidnaps Fornell's daughter Emily as leverage for the money taken from the storage unit. Patrick demands that Bishop drop off the money to him by herself in exchange for a phone that he would call with instructions on retrieving Emily, but when the exchange happens, Bishop realizes the phone is defunct and quickly puts the pieces together to determine that Emily is hidden in a van nearby. The team is able to track down Patrick as Emily had slipped a bluetooth-enabled watch in the bag containing the money. Throughout the case, Diane and Fornell consider the ramifications of giving their relationship another try and finally ask Gibbs for his blessing.