This episode also marks the debut appearance of future NCIS team member, NCIS Special Agent Timothy McGee.
At the Norfolk Naval Base, two workers later discover the partially dissolved corpse of a submariner in a barrel of acid, prompting the NCIS team to be called to the scene where they work with the Base Agent in charge to investigate the circumstances surrounding the submariner's death. Gibbs soon suspects that the killer is on board one of the submarines under the victim's own name, forcing himself and Kate into a race against time to find and identify the impostor before a potentially devastating biological attack occurs...
As a result, Walters begins moving some drums onto the end of a truck for Jeb but gets a little hasty, causing the drums in question to fall to the ground with the lids opening.
While Walters comments he's going to be cleaning this stuff up for days, the two are shocked when they see an acid-dissolved body sticking out from one of the drums.
In the bullpen, NCIS Special Agent Anthony DiNozzo Junior is talking to an unidentified person named McGee who he tells to secure the scene and wait for the team to get there.
He then hangs up and that the Norfolk Case Agent sounds pretty green.
It then shows Caitlin Todd who is also getting ready to go and Tony remarks if she's coming down with something, then she shouldn't sit next to him in the truck.
"There's an upside to having a cold?", Kate snaps.
Leroy Jethro Gibbs arrives and asks if they're ready.
Unfortunately, in her haste, Kate knocks over Gibbs's coffee cup and Gibbs isn't sure how to react.
Seconds later, Gibbs then stomps off, telling the other two he'll meet them in the truck.
As Kate begins cleaning up, Tony remarks that he's never expected Gibbs without his morning coffee and also warns Kate that they're in uncharted waters here.
As Kate takes photos and Tony and Gibbs examine the remains, Agent Timothy McGee stands behind them, wearing a surgical mask and trying to make himself look as if he isn't there.
Gibbs eventually dispatches DiNozzo to send the young Agent and DiNozzo asks McGee to help him take measurements for the sketches.
Ducky then explains the properties of hydrochloric acid and believes that the body was in the acid for less than twenty-four hours given the extent of damage inflicted on the body.
There's also a mark on the arm which Kate believes might be a birthmark.
When she suggests using the Armed Forces DNA registry, Gibbs remarks that they're backlogged and that won't be anything from them for the next 48 hours.
When Gibbs leaves the scene, he grabs a box that Agent McGee just happens to be sitting on.
DiNozzo comes up and McGee remarks that he's heard stories about Gibbs with Tony telling that the trick is to figure how half is true.
At the entrance to the Norfolk Naval Base, Gibbs is interviewing a Crewman (Sub Rosa) who tells him they didn't get the victim past them in the trunk of a car.
Gibbs realizes that whoever killed the victim had to have clearance.
Outside the main gate, a group of protesters aka whale-huggers are walking in a circle, chanting "Save the whales" and "Stop sonar testing".
Gibbs asks the guard if he's shot any of them.
The guard admits that he has been tempted.
Later that night at the crime, McGee and Kate are busy putting the gear away in the truck where Tony announces that NCIS must have full control of the scene before Gibbs clears it.
Unsurprisingly, McGee takes the bait and agrees to stay as Tony and Kate walk off with Kate berating Tony for abusing his position.
Tony simply ignores her and states that since McGee's a newbie, it comes with the territory.
The two then make a remark about college with Kate saying she was a lot of fun in college.
"Really?", Tony asks.
The next morning, the team in Norfolk along with McGee have a video-conference with both Ducky and Abigail Sciuto.
Ducky tells them that the victim died from blunt force trauma to the head and remarks that the fractured skull the victim suffered gives every sign of that.
Abby then reveals that the mark on the victim's arm which Kate originally thought was a birthmark is actually a tattoo that was burned away by the acid.
Gibbs figures that the victim was a submariner and then asks McGee for the number of subs currently in port.
While this goes on, Ducky rambles on and on about the history of tattooing much to Gibbs's own annoyance.
After much searching, McGee produces the list and tells Gibbs that there are five submarines currently in dry dock and that the USS Philadelphia left at 0600 this morning.
Gibbs wants a copy of the alpha rosters which McGee goes to do and Ducky's lecture continues, causing Gibbs to roll his eyes in annoyance.
Out on the docks of the Base, Gibbs, Tony and Kate are discussing the fact that the body was probably placed in the acid to make sure that the identity was removed.
McGee arrives with the alpha rosters and confirms that everyone on all the ships including the crew of the U.S.S. Philadelphia are all accounted for.
Gibbs, on the other hand begins to believe that someone might have taken the dead man's place and his identity on one of the subs with Kate realizing that an impostor might be on board.
Gibbs then insists that the team go talk to the submarine squadron commander although McGee tells him to avoid Captain Veitch who can be difficult.
Gibbs gets into McGee's personal space and wonders if McGee doesn't think that Gibbs himself can be difficult.
"I'm sure you can, sir", McGee whispers.
Gibbs smirks in amusement before leaving with Kate and Tony following after him. McGee looks around for a few seconds and then follows.
In his office, Veitch is denying that someone could slip on board a sub as an impostor and describes the threat as preposterous.
Gibbs on the other hand believes that the threat is real and that it should be investigated. He also wants the Philadelphia called back but Veitch refuses, stating that the submarine is on its way to a NATO training mission.
Gibbs then demands that he and Kate be sent to the sub so that they can conduct their investigation on board.
Veitch then throws a hissy fit about women being unable to go on board submarines simply because they're problematic.
Gibbs has Kate and Tony leave before kicking up a huge fuss in regards to Kate. He explains that she was previously attached to the Presidential Protection Detail on board Air Force One and that she's been trained as a profiler.
Unfortunately, those glowing abilities do not impress Veitch and he still insists that women cannot be let on board a submarine.
Outside, Kate is seething and when Gibbs emerges, goes into a rant about how she's more qualified for the investigation than Tony is and that replacing her would not be in the best interests of the case.
Gibbs eventually tells her in no uncertain terms that she's going and leaves.
"Don't forget to wax", Tony replies.
It then cuts to Kate who simply gives him a sarcastic smirk before heading off.
Upon grabbing what they need for the investigation, Gibbs and Kate get a plane to an aircraft carrier, presumably that of the USS Enterprise where they meet a Air Transport Officer who welcomes them to the Enterprise and apologizes for their very short stay before telling them their helo's standing by.
The two are then riding a boat and Kate gets a surprise when the submarine emerges from underwater.
Once Gibbs and Kate are on board, they meet Commander Robert Peters who agrees to help but they're about to undergo an Anti-Submarine Warfare exercise against one of the other submarines, the USS Augusta and Peters mentions that he's interested in winning because he has a bet on the Augusta's commander involving a bottle of Stoli.
In her lab, Abby is busy rebuilding a model of what the dead submariner looked like before the acid dissolved his body. Ducky arrives and the two debate on whether he's going to turn out like Cary Grant or Hugh Grant.
Abby then tells Ducky she's studied the dead man's stomach contents and found that his last meal was a Big Mac and fries although Ducky expresses dismay, stating that probably half the Naval Base ate McDonald's for lunch and he had hoped it was something exotic like tandoori.
Abby then states she now knows what's in the McDonald's Special Sauce much to Ducky's amusement.
Back on board the submariner, Gibbs and Kate are interviewing their five suspects. They begin with Petty Officer Drew who can't tell his right from his left yet.
Drew also claims to be from South Boston but has no accent.
They then interview Petty Officer Thompson who tells them he graduated from high school a year later due to mono.
Once the Petty Officers are gone, Gibbs and Kate compare notes and realize that they've got nothing.
Gibbs talks to Commander Peters in regards to how the ship could be harmed from the inside and unsurprisingly, Peters demand they leave.
Gibbs states they'll go when they're done.
In her lab, Abby's finished working on her computer model and she emails the photo to Tony before saying hello to McGee.
Overcome, McGee asks what Abby looks like despite having seen her on the video-conference only yesterday but Tony tells McGee that Abby's out of his league and sends him off with the photo before smirking.
On the submarine, they've located their target.
In the small room, Gibbs and Kate are going over the five men again but Kate states that there's no way it could any of the five men they've spoken to.
Gibbs on the other hand believes it as the killer went to great lengths to make sure that the body didn't have any features when it was found and that whoever murdered the submariner had twenty-four to forty-eight hours to do whatever they were planning.
Gibbs then realizes that the person responsible has either worked in personnel or he has an accomplice who altered the service record before they or Commander Peters got it.
With that, Gibbs takes off.
It then cuts Kate who stares after him.
Gibbs then storms into the main center of the submarine and orders the sub be taken to a depth level so that he can talk to Tony. Commander Peters grudgingly agrees and Gibbs contacts, discussing his suspicions in regards to the service record before dispatching Tony to investigate.
Ducky arrives in Abby's lab with good and bad news with Abby remarking that she hates payback.
The first news is that there's no DNA match on the body because the Armed Forces registry computers are still down but he knows why the image of the dead submariner didn't match any of the five photos and gives Abby an idea, causing her to realize that she'll check in regards to the five suspects's previous deployments.
Tony with McGee in tow has arrived at the Norfolk Naval Personnel Office and while Tony's busy interviewing or rather charming Lt. Connors, McGee is scribbling down notes.
Upon being asked if anyone had quit recently, Connors tells a man named Joshua Fox quit two months ago and that he transferred out of Personnel a month again.
Back on the submarine, the Chief of the Boat in consulting Drew in regards to the Augsta but Drew doesn't have anything. The COB is bitter, muttering "Damn NCIS" under his breath.
In the room, Gibbs is forcing Kate to drink water because he wants to go interrogate Petty Officer Thompson again.
Kate lures the COB out, giving Gibbs a chance to sneak out of the room.
Meanwhile, Tony and McGee arrive at Joshua Fox's address and prepare to investigate.
Back on the sub, Gibbs is interviewing Thompson who admits that he'd been in juvie and that if the Navy found out, he'd never seen the inside of a sub.
Unfortunately, the COB figures out things and drags Gibbs back to the room where he berates the two Agents before leaving with Kate remarking if that effect is because they're NCIS or is just Gibbs.
"I like to think it's me", Gibbs admits.
Abby talks to Ducky and tells him she didn't get anything from the photos. However, when Ducky unknowingly gives her a hint, she goes to investigate further.
In Fox's place, Tony and McGee have broken in and are busy searching for something but the place is empty.
They eventually find a huge bookshelf before moving it aside and flinging the door open, Tony and McGee discover that the room is full of anti-Navy sonar information and the computer even has a screensaver of a whale destroying a submarine by biting it in half.
DiNozzo just stands there.
It then cuts to McGee who's examining the room, curious.
Using his computer skills, McGee uncovers information strongly suggesting Fox is an eco-terrorist looking for revenge for the whales who have been killed by Navy sonar devices.
Tony then finds a tiny canister which McGee realizes could have a sarin gas and when Tony asks if it was introduced into the air conditioning system, McGee grimly states that it could kill the entire crew.
On the submarine, a message has arrived regarding the impostor along with the threat of sarin gas.
Commander Peters reads it, orders the air conditioning be shut off so that the engineering team can go through it before he sends the COB to go get Gibbs and Kate.
Peters then orders an emergency blow and the submarine goes into overdrive.
In the room, Kate finds herself being thrown up against Gibbs who tells her there's an emergency blow.
The COB arrives in to get them and orders them to hang on just the submarine breaks the surface.
Finally, everything settles down again and Kate remarks, "Wow".
"Yeah, that's what they all tell me", Gibbs replies.
Kate slaps Gibbs before he leaves for the bridge. She then stops to give the COB an evil eye before following after Gibbs although the COB is still grinning to himself.
Abby has found what she's looking for because she remembers she was absent the day a science club she belonged to took their photo.
She shows Ducky a photo of the real Petty Officer Drew (Sub Rosa) and when she states he's a sonar operator on the Philadelphia, Ducky states that he isn't because he's lying in Ducky's cold storage and the two figure out that it's an impostor.
Meanwhile, the impostor Drew who's aware that he's busted requests permission for a head call which is unknowingly granted.
As he leaves, Gibbs and Kate arrive, getting their first message from Tony and then a second from Abby which confirms without a doubt that the fake Drew is the impostor.
Peters gives the message to Gibbs and Kate and then asks for Petty Officer Drew.
Gibbs, Kate and Commander Peter head to the bunk to confront the impostor but when Gibbs pulls the curtain aside, they learn that Drew has managed to kill himself by suffocating himself with a plastic bag while removing his uniform.
A while later, Tony then calls Gibbs and Kate, informing them that the dead fake Petty Officer Drew was a man named Sean Travis who was a sonar operative and served on a few attacks subs before being dishonorably discharged.
Commander Peters announces that the submarine's heading back to Norfolk and then orders that the submarine be dived back down underwater.
When Kate asks, he tells her that submarines can go at a much faster speed underwater than on the surface and also states that the air conditioning system will be kept off.
Peters states that he intends to do just that and that it's going to get hot in here.
"Ah, used to taking heat", Gibbs states.
For the first time, Peters smirks.
Tony arrives back at NCIS HQ and brings the canister prototype to Abby who examines it.
While doing so, the two have a talk about McGee and Abby then realizes that it has a bi-metal trigger which can be sent by either heat or cold. She runs a quick test on it and finds the canister in question responds to five degrees centigrade which means that whatever's on board will be released.
When she asks what it is, Tony states it's sarin gas, causing Abby to remark, "Nasty".
Abby also tells Tony that the air conditioning system or freezer could be just right for that to happen before she gets back onto the topic of McGee when she asks Tony if he's cute.
Tony responds by stating, "Can a guy be cute to you without body art?".
"Sure", Abby replies. "I'm not a snob".
Back on the submariner, Gibbs is pondering about the sarin gas not being released. Kate dismisses it, stating that Drew never had a chance because he was kept in isolation.
When a Mess Specialist arrives with ice cream for them, Gibbs figures out that Travis didn't commit suicide to give up.
It was his back-up plan all along.
Upon entering the freezer, Gibbs tells the COB that Travis bobby-trapped himself by swallowing the canister before dying. He opens the body-bag and Kate realizes with horror that the gas has also been released.
Gibbs realizes that if the gas gets out, then they're all going to die before ordering Kate to get tell Peters while also stating that there's only way to get Travis off the boat in a hurry.
Gibbs and the others arrive at the torpedo room and stuff the bag into an empty torpedo tube.
Eventually, the all-clear is given and Travis along with the sarin gas both get the endless ocean as their eternal grave. Soon, Gibbs requests that the ice cream be put back in the freezer.
Kate arrives back in HQ, bearing a USS Philadelphia cap. McGee arrives with his report and Tony reveals that McGee went to MIT with Gibbs adding, "And Johns Hopkins".
Upon being prompted, McGee informs them that he's got a lunch date with Abby but Tony is amused by the whole thing, offering to take him down to the lab.
At the elevator, Tony yet again states that McGee is not Abby's type but McGee silences him by hinting that he got his ass tattooed and went with "Mom", Tony is left standing there, open-mouthed just as Gibbs and Kate glance at the scene unfolding before them.
When Kate figures out what's left Tony speechless, Gibbs tells her that McGee got a tattoo.
It then cuts to Kate who is watching the elevator with a look of amusement on her face.
- Timothy McGee, an NCIS Special Agent assigned to the Norfolk Naval Base is introduced for the first time.
- There is a New Jersey Devils ice hockey game on the TV while Gibbs and Kate are eating ice cream. They were playing the Philadelphia Flyers- the Devils had just scored. Soon after, there is a quick shot of play in the corner of the rink.
- In both "Sub Rosa" and the Season 2 premiere episode, See No Evil (episode), when both the sub and the office building have no air conditioning due to the fact that it has been switched off or was broken, Gibbs is seen drinking coffee and Kate asks how he can do that. He gives two different answers - it helps him think and keeps him cool, respectively.
- McGee asks DiNozzo what Abby looks like, saying that she "sounds cute". However, he was in the room when Gibbs, Tony and Kate were having a video conference with Abby and Ducky but it could be presumed that he probably didn't know her name because the others didn't tell him who she was.
- In an interview Michael Weatherly stated that the 'dance' he did before tossing the rock through the window was an ad-lib and that he did it as a tip of the hat to Mark Harmon who used to play football. It was also one of the first times he ad-libbed.
- The song playing in the lab while Abby is busy informing Tony about the canister he discovered in the suspect's house is "Euphoria" by Collide. Interestingly, Collide was the band playing in the lab where Abby was shown for the first time during Ice Queen (episode), the first of the two-pilot episodes that introduced the NCIS characters.
- This episode marks the first appearance of Timothy McGee, played by Sean Murray, who would later become an official cast member in the following season of NCIS. This is Murray's second time working on a show created by his stepfather, Donald P. Bellisario: Sean also starred in NCIS's parent series, JAG, as Danny Whelden, a teenage always causing trouble. It should be noted that Sean's mother is married to Donald P. Bellisario, thus making Sean Bellisario's stepson.
- While McGee is busy hacking into the eco-terrorist's computer, Tony says "Guess flying toasters would have been too much to ask for". The flying toaster screensaver is a famous screen saver available on the Macintosh operating system.
- In the scene just after Tony gives Abby the tiny canister and they're walking into the main lab, the reflection of a crew member backing out of the room can be seen in the glass doors.
|Leroy Jethro Gibbs||Mark Harmon||An NCIS Special Agent in charge of the main NCIS Major Case Response Team.|
|Anthony DiNozzo Senior||Michael Weatherly||The Senior Agent of the main NCIS Major Case Response Team and also the second-in-command.|
|Caitlin Todd||Sasha Alexander||A Secret Service Agent previously assigned to the Presidential Protection Detail on Air Force One and who is now an NCIS Special Agent as well as Tony DiNozzo's partner.|
|Abigail Sciuto||Pauley Perette||A Goth who is also the Chief Forensic Scientist for the NCIS Major Case Response Team.|
|Donald Mallard||David McCallum||NCIS's Chief Medical Examiner.|
|Gerald Jackson||Pancho Demmings||Assistant Medical Examiner for NCIS.|
|Timothy McGee||Sean Murray (actor)||NCIS Agent stationed at the Norfolk Naval Base who calls Gibbs and his team for help in investigating the gruesome discovery of a melted body in a barrel of acid.|
|Chief of the Boat||Peter Onorati||A Navy Officer assigned to the USS Philadelphia.|
|Robert Peters||Glenn Morshower||Commander of the USS Philadelphia.|
|Veitch||Ben Murphy||Captain of the Norfolk Naval Base.|
|Akron||Michael Lowry||A man presumably assigned to the USS Philadelphia.|
|Crewman (Sub Rosa)||James R. Black||A security guard assigned to the Norfolk Naval Base.|
|Thompson||Eric Ladin||A Petty Officer on the USS Philadelphia.|
|Sean Travis||David Monahan||An eco-terrorist posing as Petty Officer Drew.|
|Connors||J. Robin Miller||A Lt. stationed at the Norfolk Naval Base.|
|Mr. Walters||Mik Scriba||A dock worker at the Norfolk Naval Base.|
|Jeb||David O'Donnell||Waste Specialist.|
|Air Transport Officer||Reed Rudy||An officer on the USS Enterprise who had a brief talk with Gibbs and Kate who were on their way to the USS Philadelphia.|
|Mess Specialist||Mat Hostetler||An officer of the USS Philadelphia who delivered ice-cream to Gibbs and Kate.|
|Seaman Apprentice||Jamie Moss||A man presumably assigned to the USS Philadelphia.|