The Elmo Ziller Story - S2-E20
Plot hole: Considering the reveal about 2/3 into the episode, Higgins appearing to Magnum coming down the stairs of the estate at the beginning does not make sense. Spoiler; it is revealed that he was Elmo all along, but then he would have had - with his terrible athletic ability as shown in previous episodes - to run across the estate beating Magnum to the villa or somehow find a way to the top floor that is never shown throughout the whole series, change clothes and - with the lads! - come down without breaking a sweat.