I read chapter five. Now, why is the Doctor's attempt to parlay with the Tigers at the spaceport the crucial moment? Because of the threat the humans holding the 'port now pose - but this isn't made clear, either to the humans or the reader.
I still love the bit where the Doctor pisses off in to the Bewilderness. I think it needs to be explained better, either at that moment, or later: he's tried forging a peace from the human side of things, now he's going to try from the Tigers' side, leaving his companions in the city both for their safety and to prevent Quick from really screwing up. He's profoundly hurt because he doesn't fit in - not with Karl in the orchestra, or with Quick in the Movement. Later, he discovers he doesn't fit into the Tigers' world either. He's also in a profoundly bad mood, which I hugely enjoyed writing. The anti-Smurf.