Enemy on the Hill is the fourth episode in Season Nine of NCIS and the 190th of the series as a whole.
The team must find out who hired a hit-man to kill a Navy Lieutenant Commander while Abby goes through a series of tests and uncovers some startling secrets concerning her own family history which leaves her stunned.
In the bullpen, with a photo of Paul Marvin Arliss now on the monitor, McGee remarks that it's hard to believe that the guy was an infamous killer and that up until yesterday, Arliss's only claim to fame was a Salesman of the Year as a manufacturer's rep for a furniture company.
"He evaded the FBI for years by hiding in plain sight", DiNozzo remarks before stating that in a weird way, you've gotta admire the guy.
Gibbs arrives into the bullpen and responds by headslapping DiNozzo before stating that Arliss is a mass-murderer.
|Leroy Jethro Gibbs||Mark Harmon||Special Agent in charge of the Major Case Response Team, NCIS|
|Anthony DiNozzo||Michael Weatherly||Senior Special Agent, MCRT, NCIS|
|Ziva David||Cote de Pablo||Junior Special Agent, MCRT, NCIS|
|Abigail Sciuto||Pauley Perrette||Chief Forensic Specialist, NCIS|
|Timothy McGee||Sean Murray||Special Agent, MCRT, NCIS|
|Leon Vance||Rocky Carroll||Director of NCIS|
|Donald Mallard||David McCallum||Chief Medical Examiner, NCIS|
|Detective Danny Sportelli||Jack Conley (actor)||Homicide Detective with Metro PD. Conley previously appeared as Detective Sportelli in the Season 7 episode, The Inside Man (episode).|
|Special Agent Thomas Survoy||Morocco Omari||Special Agent, NCIS who previously appeared in the Season 3 episode, "Boxed In".|
|Lieutenant Commander Geoffrey Brett, USN||Brett Tucker||U.S. Navy.|
|Nicholas Sandlock||Michael B. Silver||A man who appears in the episode.|
|Drew Turner||Melissa Ponzio||Financial Planner.|
|Mrs. Roach||Shannon Wilcox||A woman who appears in the episode.|
|George Kaplan||Brett Tucker||An alias for Commander Brett and unseen decoy identity. This is a reference to the 1950s movie, "North by Northwest".|
|Kyle Davis||Daniel Louis Rivas||Abby Sciuto's biological brother.|
|Samantha Tate||Sibila Vargas||ZNN Reporter.|
|Female Passerby||Karly Rothenberg||A woman who appears in the episode.|
|Paul Marvin Arliss||Kevin Cotteleer||A man who is actually a contract killer. Dies from injuries sustained after he was hit by a bus.|
|Afghan Teacher||Sara Faiella||Uncredited Role.|