While investigating the death of a petty officer, people at the office prepare to usher Ducky off of the NCIS coil.

Palmer cannot wrap himself around the perfect gift to get his mentor, who is being regaled all of the place.

Petty Officer's white was tampered with so now it's time to find out who did it. PO Harper was doing his own search into the gear, so it's probably not him.

The sub was directed to drive while NCIS was on board. Uh oh. The Pentagon is on the phone contacting Director Vance.

The USS Memphis is gone. Gibbs and Bishop might have just gotten kidnapped.

The duo doesn't seem to have any idea what's going on.

Bishop wants to believe Gibbs is as panicked as she is, but he's not biting.

McGee and Torres try to investigate a storage locker, but the unit is on fire, deliberately set.

The Galley guy gave White the book on electrical subsystems. The COB told the cook not to tell anyone, but that was before White was killed.

A guy named Walter Miller disappeared after shutting down his life. He was the owner of the storage unit. Miller had a blog on which he decided that the US needed to launch a pre-emptive war before it's too late.

Miller should not be conducting any business on a nuclear sub.

The COB isn't quite forthcoming when it comes to answering the questions from Gibbs and Bishop. She locks Gibbs and Bishop into a room so they don't interfere with their command.

A device was planted by Miller that jams all incoming signals but his own, and if NCIS doesn't find the device he's using to communicate, the US Govt will sink the submarine before it starts a war with Russia.

Long story short, the find the guy, send a correct signal and save the day. 

Ducky will be the new NCIS Historian. He can come and go on his own terms.