[Spoilers ahead ... ]

First, we get to the meet the original Cleon.  Dawn and Dusk call him forth in their (mainy Dusk's) need to find out if Day has edited Dawn and Dusk's memories.  Dusk provides a good succinct explication of their dilemma: if their memories were really altered, how would they would they know that?

The original Cleon is of course played by Terrence Mann, who plays Dusk, and he does a good job of it.  The original Cleon has a vibrance, a presence, a wisdom, that Dusk doesn't have.  Other than that, the original offers no surprises, urging Dawn and Dusk not to rock the boat.  But now that we the audience know that the original Cleon can be summoned, that adds a powerful resource for the Cleonic triad.

The other great discovery is made by Sareth's family:  Demerzel is a robot!  We of course already knew that (from earlier episodes in the TV series, and of course from Asimov's novels). And the Cleon clones know Demerzel is a robot, with warm, organic flesh -- indeed, in tonight's episode, Demerzel reassures Dusk that she would have memories of everything, even if Day somehow edited some out of Dusk and Dawn's minds.  

But speaking of Asimov's novels in a review of this episode of the TV series, it needs to be mentioned again that Demerzel was a male robot in the novels, who basically gets Hari Seldon started on psychohistory, and gets Dors (a female robot) married to Hari, where she continues as his protector.  If this sounds more intriguing a story than what we've seen of Hari so far on the screen, I'd say that's because it is.  At this point, the Seldon story still hasn't come close to what's happening on Trantor, but I continue to watch in hope.

See also Foundation 2.1: Once Again, A Tale of Two Stories ... 2.2: Major Players ... 2.3: Bel Riose and Hari

And see also Foundation 1.1-2: Mathematician, Man of the People, and Cleon's Clones ... Foundation 1.3: Clonal Science Fiction, Hari Seldon as V. I. Lenin ... Foundation 1.4: Slow Hand, Long Half-Life, Flipped Coin ... Foundation 1.5: What We Learned in that Final Scene ... Foundation 1.6: Folded Variations ... Foundation 1.7: Alternate History/Future ... Foundation 1.8: Divergences and Convergences ... Foundation 1.9: Vindication and Questions ... Foundation Season 1 Finale: Right Up There