The occasion is Cesare in the court of the King of France. He's there to give the king an annulment tendered by the Pope - not, it turns out out, because the king's wife is so ugly as his ambassador told Rodrigo, but because she hasn't given him any children. And the grateful king rewards Cesare with all manner of worldly benefits, including a wife.
This is a big favor indeed, because Cesare, after all, may be the son of the Pope, but he's still a bastard. Charlotte D'Albret is not only attractive but high-born, and her marriage to Cesare is a good move for all kinds of reasons, including that the two enjoy each other in bed. With all the near-insanity swirling around in The Borgias, it's nice to see a couple in good old fashioned lust and contentment, especially when one of the partners is the long-suffering Cesare.
But the political implications are powerful as well. With the more than able Catherina Sforza putting together on alliance of Italian city states against Rodrigo, the Borgias will need all they help they can get. Cesare talks the French king into giving him an army, which will make for a high stakes historic battle before the season is over.
Michelotto is also doing his part in Naples. Lucrezia's set to poison the King of Naples who won't let her keep her baby. Michelotto has a better way, and dispatches the King with a shove into a pond with lampreys. With no one at hand to see Michelotto shove the King into the water, his death will goe down as due to horrible natural causes.
In the muti-dimensional superbly played chess game which is The Borgias metier, Cesare and Michelotto continue to make the best moves.
See also The Borgias Season 3 Premiere: "Blade's Breath" ... The Borgias 3.2: Going Both Ways ... The Borgias 3.4: Incest and Debauchery
And see also The Borgias Season 2 Sneak Preview