Book 4 is called The Candle In The Wind. And, no: it's not referencing the Elton John song.
And now a number of years have gone by. Agravaine is now 55, but looks much older.
He's hanging with his bro, Mordred, at their lux castle in Camelot.
Mordred is trying to get some stuff started with Arthur—to overthrow him, apparently—but Agravaine is pointing out that no one fights over private drama anymore. That's so last century. Now, it needs to be a national beef to get people stirred up.
Besides, the whole private thing is much too complicated, and no one's going to get whipped up in anger about something that'll take over a half hour to explain.
In the middle of this, though, we find out that when Mordred was born, Arthur put him on a boat and sailed him into the water, presumably to drown him.
The big problem here is that Mordred, being illegit, can't very well rouse up the people against Arthur for sleeping with his half-sister when he, the illegit guy, is the one doing the rousing up.
Also, as Agravaine points out, the people just love Arthur. He's their guy.
The conversation turns to Lancelot, and how he's knocked them off their horses in various jousts over the years.
It's also well known around the Court and everywhere else that Lancelot and Guenever are sleeping together behind Arthur's back.
Even Arthur knows (he's been told three times, although in roundabout ways), but doesn't do anything about it.
Agravaine wants to accuse Lancelot openly, and let him take his chances in the newfangled Law courts, since there's no more trial by battle (which Lancelot always won).
If Arthur had to investigate this accusation, though, their bromance would be broken up, and the power of the Court would be divided. This would give all the discontents of the kingdom a chance to rise up, and then Agravaine and Mordred could both have their revenge.
We get a "the story so far" kind of montage that reminds us of the background of the G-boys, going all the way back to the kidnapping of Igraine by Uther Pendragon, and how Arthur fits into the picture.