The centerpiece of Episode Two is obviously the first meeting between The Doctor, Romana, and Duggan and the Count and Countess Scarlioni. Has there ever been a better scripted scene in Doctor Who? So many lines and passages from this scene have continued to live on in Doctor Who lore, quoted ad infinitum by fans far and wide.
"What a wonderful butler! He's so violent!"
"You're a beautiful woman, probably."
"I don't think he's as stupid as he seems." "My dear, nobody could be as stupid as he seems."
And so on, and so on. I outlined earlier how invincible The Doctor and Romana had become to the point that the Daleks were no longer considered formidable. What was needed for Doctor Who to become interesting again was an enemy that could match, or even top, our heroes, and, in Julian Glover's Scaroth, we have it. Glover is magnificent in this, playing the ultimate James Bond villain (a couple years before he became a Bond villain) without ever going over the top. In a story where there are so many entertaining and fascinating characters vying for, and receiving, adequate screen time, it is possibly Glover who is the most watchable.
I've spoken in the past about how Episode Three is often the most difficult installment to maintain momentum in a four-part story. But the cliffhanger to Episode Two, with the twist revelation of Scaroth in Florence in 1505, ensures that Episode Three will be an entirely new beast in a story that has already been enthralling to watch.