Baltimore (NCIS)

The serial killer nicknamed the "Port to Port Killer" (last referenced in the prior episode "Two-Faced") strikes again, leaving his victim dressed in an Admiral's uniform at the Navy Lodge in Washington, D.C. Anthony DiNozzo (Michael Weatherly) is jolted to recognize the victim as Danny Price (Scott Grimes), his former partner in the Baltimore Police Department's homicide squad.

The two detectives first met Leroy Jethro Gibbs (Mark Harmon) when the latter came to Baltimore on an undercover assignment, linking a Navy officer to a money laundering scheme.

Equally unable to continue working with him, DiNozzo considers quitting the police force, but Gibbs, impressed by his abilities, invites him to join NCIS.

Price had realized that the money launderer never exposed him because there was a second, higher-ranking accomplice in the Department — his and DiNozzo's former captain, who killed Price to keep his corruption secret, then disguised his crime as an act by the Port to Port Killer, using details from Ducky's report, which had been emailed to the Baltimore Police by NCIS.

Gibbs and DiNozzo arrest the captain, but Ducky and Abby (Pauley Perrette) announce that they have a worse problem: the email alerting Ducky to the typo in his report did not come from Abby, as he first thought, but from the Port to Port Killer himself, who not only knows that NCIS is tracking him, but has access to their internal records and computer system.

On 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".

[3] Tim Kelleher returns in a flashback as NCIS Special agent Christopher Pacci, a former colleague who was last seen in Season 1 episode "Dead Man Talking" where he was killed in the line of duty.

[6] Julian Spivey from Examiner.com included "Baltimore" in his compile of the "10 greatest episodes of 'NCIS'" in January 2012, saying, "I don't think there has been another 'NCIS' character that has matured as much in the series' nine seasons as Michael Weatherly's Tony DiNozzo.