Two Navy patrols encounter a group of men while they were stealing weaponry.
One of the Navy patrols is shot dead, and his partner severely injured. One thief is mortally injured. Dr. Taft is unable to save him during surgery.
Taft notices a bad scar on the thief's left arm.
Abby determines that he had a titanium plate in his arm, that was designed for femur bone (leg). She tells Gibbs it was manufactured in 1995 and that it was originally implanted in a priest named Father Gerard Carlin, now deceased.
Tony reveals that Father Carlin is presumed dead, after having gone missing in South Sudan in 2003.
McGee and Bishop visit the injured Navy patrol in hospital - Petty Officer Janet Shor. They encounter ATF Agent Earl Kitt, who was finishing up his interview with her.
Tony and Dr. Taft visit Jeanne and her husband Dr. David Woods to investigate doctors working in the Sudan.
Ducky finds a bullet lodged in the spine of the dead thief. Abby traces it back to Jeanne's father, René Benoit.
Jeanne identifies one of the thieves as a guy named Pierre. He used to be a driver for her father.
McGee identifies a man he thinks might be Pierre. His last name is Oskar.
The team storms Oskar's house, only to find him murdered. The ATF storm the house while the NCIS team is still there.
Taft takes his wife out to the movies. They walk out to the car. Taft gets a call so his wife decides to get in and get the car started so it can warm up.
She finds she can't start it, so she gets out to tell her husband. As they're walking back to the car, it explodes.
McGee and Bishop tell Gibbs that Agent Kitt told them the guns are on their way to the Ukraine. They assume the third thief is on the same plane.
McGee tells Gibbs that Kitt said they'll take the case from here and keep NCIS in the loop. Gibbs says he'd rather hear that in person.
They bring Kitt down to NCIS to be interviewed by Gibbs.
Kitt tells Gibbs he's been running a top secret operation. He says guns have been going missing for years, so they decided to install a tracking mechanism in them. Rather than scoop up the guns, they've been tracking them to see where they're going.
Kitt helps the team track down the third thief. They use a tire-spike to blow the front wheel of his car. He gets out and opens the back door to grab a gun. The team close in on him and arrest him.