When a Marine, Brandon Valdivia, is thrown off the patio roof of a trendy downtown hotel, NCIS must unravel several mysteries around his death. Examining Valdivia's financial history, Kensi and Dom determine that he and his co-worker, Alex Walder, were involved in a counterfeit money scheme and Secret Service Agent Natalie Giordano arrives to assist with the case as it connects to a counterfeit distribution network she's been tracking. She's also hoping to make a more personal connection with Callen but he's not going to violate his "no law enforcement" policy when it comes to dating. NCIS tracks down Alex Walder and learns that Valdivia and Walder were making counterfeit bills with plates they found when they were stationed in Bagdad. Walder believes that their printer killed Valdivia and is after him so Kensi and Callen go undercover to collect evidence on the printer. When the "buyer" of the bills shows up, they're shocked to discover it's the Marines' Sergeant: he killed Valdivia. His plan was to ship the fakes to Iran for distribution in the military, keeping the real money that was being sent for him.