‘House of the Dragon’ episode 4: Who is the White Worm?

So, the latest House of the Dragon episode was a lot.

But now that the dust has settled on all that backstabbing and incest, we need to retrace our steps and work out exactly what was going on.

Who was informing on who? What was the motive? And who is the White Worm, who sent that messenger to Otto Hightower?

Let's take...