A group of marines runs down the beach in formation, but one breaks off when he sees something. He calls his sergeant over. There's a dead Marine in the sand in scuba gear.
Tony rifles through his desk, looking for the van keys. He remembers that he got pizza and threw out the box. Time for some Dumpster diving.
And that's when Gibbs comes to announce the dead body. He found the keys in the elevator.
On the beach, Tony razzes Palmer about his super hot embalmer girlfriend.
The victim is a Navy diver, Lt. Michael Jenson. Duckie finds the victim's left forearm was sliced off by a boat propeller - after his death. He died three or four days ago.
He was on leave.
Duckie finds a puncture wound through his wet suit. They think whoever he was diving with stabbed him and left him to die.
Tony and Gibbs go to Jensen's house and find the door ajar. Inside, a woman with a gun sneaks up on Tony. And then a man gets behind Gibbs. They're Coast Guard Investigative Service, smaller than NCIS, but with broad jusrisdiction.
Back at the office, Gibbs chats with his female counterpart Agent Abigail Borin. She thinks it's her case because Jensen could be her killer. They found a boat captain dead on a salvage ship and security footage of him earlier with Jensen.
Gibbs says he'll call her if he finds anything.
Down in the morgue, Duckie says he hasn't yet been able to positively ID the body as Jensen. He drowned.
Gibbs heads to see Abby and finds her shaking a laptop furiously. She has nothing. Jensen had Nitrox left in his tank and his computer has security she can't crack. She takes a hug and a Caff-pow from Gibbs and gets back to it.
Tony reads up on Borin, and finds she is a former Marine. She reminds him of Gibbs.
She sneaks up on him.
Ziva mentions an odd charge to Jensen for a storage facility in Virginia.
Borin joins Gibbs in MTAC and they video conference with a lab tech. She reports they found Jensen's fingerprints all over the salvage boat.
Gibbs and Borin decide to work together.
Borin show Gibbs the GPS of the salvage boat, which was searching an area.
Borin's people are following up satellite footage of other boats in the area. Tony's tracking several large deposits to the captain's bank account and McGee finds a reoccurring phone number to Jensen's cell from Missy Dawkins. She's coming in.
McGee talks to Missy, who dated Jensen but says he didn't have a lot of money. She says he told her he was going on a hush hush navy thing and would have a lot of money when he came back.
At the storage facility, Tony and Ziva find ocean charts and news clippings about treasure hunters. There are old artifacts laying around.
Abby goes over them in her lab and meets Abby Borin. She got into Jensen's laptop and found emails to Joseph Mavrey about Calafuego, a ship Jensen was researching.
Gibbs and Borin go to Mavrey's house, where his wife says he's out of the country do gooding in the third world and can't be reached. She hasn't heard of Jensen. Gibbs says good bye. Borin's peeved, thinking she's covering for her husband. She wants to bring Mrs. Mavrey in based on her gut. But Gibbs wants to wait.
Tony goes cuckoo with pirate movie references as McGee looks up the Calafuego, finding it could have $200 million on it. McGee finds that Mavrey is getting sued for a stent he designed, so he'd need money.
Vance joins the group having heard from the attorney general about Mavrey's doctor group - it's still in the country and he's performing a surgery on web cam.
Gibbs and Borin go to Mavrey's clinic where a woman tells them he's not there. They find another doctor about to do the surgery. He tells them they haven't heard from Mavrey in over a week.
Back at the office, McGee finds a charge for a private jet to the Marianas Island. Borin has her people get ready to intercept it when it lands.
Gibbs visits Duckie, who's back to wearing bowties again. He broke up with Sophie. (She put some of mother's silver in the dishwasher.)
Duckie shows Gibbs Jensen's tooth mold. They are fractures that he thinks came from a seizure of some sort. He had a history of a liver condition that would have precluded diver training, unless someone changed his records.
In her lab, Abby reports a master diver would have known to switch to to oxygen in shallower water, and their diver didn't.
McGee joins them and reports they found a washed up inflatable boat on the shore. And the Coast Guard intercepted Mavrey's plane- he wasn't on it. The pilots were paid to fly an empty plane.
Gibbs sends Tony to Mrs. Mavrey's house. He brings her in.
Borin doesn't believe her when she says she doesn't know where he is. Mrs. Mavrey shows them an email he sent, saying things would be better when he got back in a week.
Tony shows her photos of the victims.
Borin threatens to charge Mrs. Mavrey as an accessory.
Duckie has Jensen's records in the lab, which show no liver condition. His staff doctor saw no indication either. Their beach body isn't Jensen.
Tony calls DC Missing Persons, Borin calls the FBI and McGee pulls Mavrey's personal medical records. He had a liver disorder.
Borin and Gibbs break the news to Mrs. Mavrey. She tells them her husband took a lot of cash out of his corporate accounts to cover the lawsuits. She thinks he put it into the treasure hunts.
McGee finds that Missy Dawkins just bought two tickets to Mexico, one for her and one for Jensen.
They bring her in. She says he never showed to meet her. Gibbs realizes she was another decoy. Missy babbles about Jensen spending all sorts of time with "that rich doctor and his wife."
Down in Abby's lab she's busy proving the gold coins found in Jensen's storage unit are fake. There was no treasure. He was conning Dr. Mavrey.
Gibbs and Borin realize Mrs. Mavrey said she never met Jensen. They think they were having an affair. They head to the Mavrey's.
They find Mrs. Mavrey and Jensen frantically looking for his $10 million. Tony shows them the cash they found in Dr. Mavrey's work locker.
As they're arrested, Mrs. Mavrey tries to pin everything on Jensen.
Back at NCIS, Vance thanks Borin and Gibbs grudgingly does as well. They shake and say their good byes.
Downstairs, Tony sets Ziva up with popcorn for a ceremonial viewing of Douglas Fairbanks in "The Black Pirate." They claim both their dates canceled as they share a Friday movie night at work.