The knight in question, Cyan Dag, is sent off on his quest by a lady Bard. It rapidly becomes evident that there's something up as the same Bard (or another one very similar...I'm not actually sure) is busy sending one of his enemies (Thayne Ysse) off on a nearby quest to fight a dragon, acquire its treasure, and use the treasure to attack Cyan Dag's kingdom. So you're thinking that actually the Bard is evil and has tricked Cyan Dag, getting him out of the way or something, while encouraging the northern kingdom (where Thayne Ysse is from) to attack - possibly in collusion with the changeling queen. So Cyan Dag is off to rescue a queen trapped in a tower, Thayne Ysse is off to challenge a dragon in another tower, and then there's a third character, Melanthys, who spends all of her time embroidering in a tower where a magical mirror is showing her glimpses of things happening far off...which she embroiders, and then leaves on the window ledge where they disappear.
So we have 3 different towers, 3 different main characters, multiple strange bard-type women who keep showing up in unexpected places and lots of very strange seeming magic. Also, all of the towers appear to be in the same place...or possibly not really existing in real locations. It all adds up to a story that feels hideously confusing at times. I'm willing to put up with a lot of that from Patricia McKillip, but this was pretty extreme. It is hard to focus on all the different aspects of the story when you don't know how they are connected or which bits are the really important ones. Especially when you're having some trouble distinguishing the characters. What kept me reading was Melanthys and her family, which initially felt like it wasn't really central to the story, but in fact wound up being very very important.
The ending was quite satisfying. Everyone's motives were explained, very important things got resolved in ways that worked and were obviously going to continue to work for a long time to come. People overall were going to be much better off. So overall I enjoyed the story, but it isn't compelling me to pick it back up and re-read it immediately, even though I'm really tempted to see if it still feels as confusing one I know where it is going (and now that I know there are actually 3 different lady Bards and not just 1 with the ability to pop around the world at will).