Episode 56 of "JAG"
s03e19 Death Watch

Mac arrives at Harm's apartment and is surprised to see that he has forgotten she was coming over and that he is getting to leave with a firearm. Stalling him, she gets him to tell her the story 2 years ago of the murder of his then-girlfriend, Lt. Diane Schonke, an Academy classmate, after her ship, the USS Seahawk docked in Norfolk. When Harm shows Mac a picture of Diane, Mac is stunned to see that Diane looks just like her. When Harm tells Mac that he believes he has finally figured out who the real murderer is (Agent Turque) and that he intends to confront him, she gets him to initially agree to take her with him. Harm however tricks her and drives off, leaving Mac behind standing in the rain. Desperate to find Harm before he does something he'll regret, Mac calls Bud to meet her at JAG. Bud was an Ensign on Diane's ship and was one of the people who found Diane's murdered body. Bud tries to help Mac fill in the gaps and helps Mac learn that Agent Turque isn't the murderer. Searching Navy records, Bud learns that the USS Sheffield docked today and that Cmdr. Hobarth is on the ship. Mac goes to meet with Harm & Hobarth, but wearing very-wet clothes, Bud offers to give her a uniform of Harriets to wear. Harm waits at the dock of the USS Sheffield until Cmdr. Hobarth leaves the ship and then confronts him. Harm tells him that he read a copy of a letter Diane had left in her personal letters (returned to him after Diane's investigation was closed) that Diane had told Cmdr. Hobarth her intent to file a grievance once they docked because when she felt she was being stalked on the ship and reported to Cmdr. Hobarth (then XO on the Seahawk), he refused to do anything official about it. Harm then tells Hobarth that he knows he killed Diane to save his career, but in the end, his career stalled anyway. As Harm moves toward Hobarth pulling his gun, Mac yells to him. Hobarth looks and sees Mac wearing a Navy uniform in the fog. Believing her to be Diane, he backs up on the dock and falls into the water, immediately being crushed by the hull of the ship. Bud goes to get help, while Harm & Mac are forever left with the question as to whether he would have killed him. Before they leave, Harm looking at Mac embrace & kiss. Mac though tells Harm that she knows Harm really was kissing Diane.