A March 1998 episode which lays a ghost - and gives Mac (and us, the audience) an insight into Harm's back-story as the third season gets into its stride.
By this point in the timeline of "JAG", Bell had settled into the role of Mac; her confusion on seeing the photographs of "Diane" in her naval uniform is well-played and genuine. In complementing this scene, Harm opens up a little with his history with Diane. Mac shows how well she is able to guide Harm's actions - diverting him from a planned course of retribution.
The scenes are well-constructed and exploit the (usually un-aired) archive material from "Skeleton Crew" (S01Ep22) - the last NBC episode of Season One, which set up a cliff-hanger which was never exploited at the start of the (CBS-managed) Season Two (whereby "We the People" began a new arc of adventures with Harm meeting Mac for the first time and "seeing a ghost").
On re-watching this episode in 2021, I noticed that, for Season two and beyond, Patrick "Bud" was dyeing his hair - he looked far better with grey hair in the "Skeleton Crew" episode.
The "Skeleton Crew" episode, which contributes 50-60% of this Season Three episode, had (obviously) been heavily cut to fit the "Death Watch" script - and the conclusions were different. If you can, track down "Skeleton Crew" for a better insight into the canon mythology of Harm and Diane.
This enjoyable episode contributes heavily to the "Harm-Mac-Diane" mythology and explains a lot. It also has set the scene for several enjoyable fanfiction stories.