S4·E21 Wilderness of Mirrors

Harm fears he's losing his mind when he begins to see and hear his deceased father. Worried that he may be going insane, Harm finally confers with his Navy psychiatrist girlfriend who tells him she's treating a Marine officer with similar symptoms and suggests that Harm isn't experiencing anything unusual for someone who's lost a loved one under stressful circumstances. But before Harm can come to terms with the visitations, he begins to suspect that there's something more sinister involved that could cost him more than just his sanity.