|Episode no.||Season 8
|Directed by||Terrence O'Hara|
|Written by||Steven D. Binder|
|Original air date||May 3, 2011|
"Baltimore" is the 22nd episode in the eighth season, and the 184th overall episode, of the American crime drama television series NCIS. It first aired on CBS in the United States on May 3, 2011. The episode is written by Steven Binder and directed by Terrence O'Hara, and was seen by 17.87 million viewers.
In the episode, Special agent Anthony DiNozzo must dig into his past as a cop at Baltimore Police District when his old partner is murdered. Also, the episode visit the first moment between Gibbs and DiNozzo, and how DiNozzo joins NCIS.
After sending the NCIS team a message in the form of the eye in "Two-Faced" - revealed to belong to a person whose identity is classified - the Port to Port Killer seems to have struck with another victim: Danny Price (Scott Grimes), formerly DiNozzo's partner in the Baltimore P.D. homicide squad. Believing that the Port to Port Killer may have a connection to DiNozzo, the team begins to concentrate on his time in Baltimore. Inconsistencies in the autopsy reports lead them to suspect there is a copycat killer on the loose, and it is eventually revealed by a mistake made by Palmer in a report sent out to law enforcement agencies that it was what gave the copycat killer the necessary knowledge to replicate the Port to Port Killer with near-perfect accuracy. Because of Palmer's mistake, NCIS is able to catch a would-be copycat before he can kill, as well as find Price's murderer - DiNozzo's former captain in Baltimore.
The episode is intercut with flashbacks showing DiNozzo's first meeting with Gibbs in which DiNozzo arrested Gibbs while he was working undercover on a money laundering case. DiNozzo joins NCIS after finding himself unable to work with Price in the Baltimore PD, but unwilling to expose his former partner.
The episode is written by Steven D. Binder and directed by Terrence O'Hara. Executive producer Gary Glasberg wanted to include and explain many little moments from NCIS' past. "So many little origin moments are sort of touched on, from Tony's wardrobe to the head slap. And it's fun, because there's nothing blatant about it. It's all very well structured and built into the mystery. And as you're going through the story, you find yourself going 'Wait a minute, they just explained one thing'. That was our goal, to come up with an origin story that presented all this information in as natural a way as possible — and sets up what Tony's and Gibbs' dynamic would be for the next decade". 
According to Mark Harmon, Gibbs recruit DiNozzo after listening to his contributions during the case. "We did a scene [...], and every bit of the dialogue in the scene is a test, as far as Gibbs is concerned. He's listening the entire time to what Tony says. And the end of the scene depends on what he says. I mean, DiNozzo doesn't know that. But the scene ends the way it does because of what DiNozzo says, and because of Gibbs' belief in him. And from that, his gut instinct is that this kid is good".  In connection with this, Gibbs' rule #5 is introduced: "Don't waste good", referring to DiNozzo wanting to quit. It's in this situation Gibbs' head slap is shown for the first time, which would be a trademark between them on NCIS. Harmon about how the head slap began, back in Season 1 episode "The Curse": "It was totally spontaneous, though I've heard a lot of people claim it! Michael was doing his thing to a young Navy female petty officer on a ship, and it just seemed appropriate at the time to bring him back toward some sort of reality, which certainly the head slap did". 
Tim Kelleher return in a flashback as NCIS Special agent Christopher Pacci, Leroy Jethro Gibbs' former colleague who was last seen in Season 1 episode "Dead Man Talking" where he was killed in the line of duty.
Rule number 5 and 35 are revealed for the first time in this episode: 
- No. 5 "Don't waste good"
- No. 35 "Always watch the watchers"
"Baltimore" was seen by 17.87 million live viewers following its broadcast on May 3, 2011, with an 11/17 share among all households, and a 3.7/11 share among adults aged 18 to 49.  A rating point represents one percent of the total number of television sets in American households, and a share means the percentage of television sets in use tuned to the program. In total viewers, "Baltimore" easily won NCIS and CBS the night, while the spin-off NCIS: Los Angeles drew second and was seen by 14.16 million viewers. It also became the fourth largest ratings for the week it aired. Compared to last episode "Dead Reflection", "Baltimore" was down a bit in both viewers and adults 18-49. 
Steve Marsi from TV Fanatic gave the episode 4.5 (out of 5) and stated that "it was a great nod to the fans, but still relevant to the present", and "episodes like this walk a fine line, but what could have been a head-slapping (and not in that affectionate Gibbs way) resolution was sold by the strong writing and acting". 
- Seidman, Robert (May 4, 2011). "Tuesday Final Ratings: 'The Voice,' 'NCIS,' 'Dancing With The Stars,' 'Glee,' 'The Biggest Loser,' 'Hellcats' Adjusted Up; 'Raising Hope,' 'Traffic Light' Adjusted Down". TV by the Numbers. Retrieved May 4, 2011.
- Willman, Chris. "NCIS Scoop: More DiNozzo/Gibbs Flashback Secrets". TV Guide. Retrieved 19 February 2012.
- Willman, Chris. "NCIS Exclusive: When Tony Met Jethro". TV Guide. Retrieved 19 February 2012.
- Mitovich, Matt Webb (May 2, 2011). "NCIS Scoop: Gibbs Reveals Another Two Rules". TV Line. Retrieved 5 March 2012.
- Gorman, Bill (April 13, 2011). "Tuesday Final Ratings: 'NCIS,' 'Parenthood,' 'Biggest Loser,' 'Food Revolution,' 'Dancing Results' Adjusted Up". TV by the Numbers. Retrieved April 13, 2011.
- Marsi, Steve. "NCIS Review: Baltimore's Finest". TV Fanatic. Retrieved 19 February 2012.