JAG - Season 3 - Eps 20: Imposter
Clark Palmer, a renegade government agent, breaks into Harm's apartment and incapacitates him. Palmer then makes a cast of Harm's face in order to prepare a mask that he can wear to pass for Harm. Palmer plans to murder the key witness in the trial at which Harm and Mac are currently prosecutors. When Harm doesn't show up for the start of the trial, Mac takes his place, leaving Bud to search for the missing JAG lawyer. When Bud finds Harm trapped in an ingeniously booby-trapped apartment, the two must find a way to escape before the assassin can carry out his plan.
About JAG

Title: JAG
First Air Date: 1995-09-23
Last Air Date: 2005-04-29
Status: Ended
Rating: 7.299/10 (from 361 votes)
Language: EN
Seasons: 11
Total Episodes: 227
Network: NBC CBS
Genres: Drama, Action & Adventure, Crime
Production Companies: Paramount Television, Belisario Productions, NBC Productions, Belisarius Productions, NBC Studios, CBS Studios
Synopsis
Harmon "Harm" Rabb Jr. is a former pilot turned lawyer working for the military's JAG (Judge Advocate General) division, the elite legal wing of officers that prosecutes and defends those accused of military-related crimes. He works closely with Lt. Col. Sarah Mackenzie, and together they do what needs to be done to find the truth.
Cast

David James Elliott
Harmon Rabb

Catherine Bell
Sarah MacKenzie

Patrick Labyorteaux
Bud Roberts