Factual error: 1968: The basement's brick wall crumbles to reveal Trask's skeleton hanging in the alcove. Only it shouldn't be. Bodies do not remain assembled once the flesh and sinew are gone. Trask's remains ought to be a large pile of bones on the floor.
Factual error: 1966: Ohrbach's, the fashion house that supplied Dark Shadows with costumes throughout its run, suffered the indignity of seeing its name misspelled as "Orhbach's" in many of the 1966 credit crawls.
Answer: It's probably episode 193 (even though the slate at the beginning says 58). It's the episode with Sam demanding that Roger return his paintings. Three clues from the Dark Shadows Companion and from the comments of Kathryn Leigh Scott and Louis Edmonds all agree that 1) Scott is in the episode and is done for the day prior to Edmonds without his pants; 2) Edmonds is wearing a smoking jacket, and 3) Edmonds is leaning on the mantle (which is actually the cabinet where the liquor is, because the fireplace mantle is too high to lean on and the bench in front of it prevents getting too close to). There are several "breaks" in the lengthy scene where commercial were probably inserted, and all of the shots are above the waist. The previously mentioned episode 54 has Edmonds in a suit and Scott isn't in the episode; episode 54 doesn't have Edmonds or Scott; and episode 86 only has Edmonds in a suit.
Lou Edmonds was a consummate actor and would not forget that he had a lengthy scene to perform. Rather, in Episode 86, Edmonds more understandably forgot that he had to perform one last 15-second scene (a simple toast). He had removed his shoes and pants before he was reminded of the final, brief shot, and he hurried back to complete it.
Charles Austin Miller