This is eerie.
I can see the dragon-sickness and the evil it wreaks in this graph from word 75,000 to 84,000. The exact trough, almost as low as our nadir of helplessness in Mirkwood, and perhaps even more hopeless, is here:
[15.032] As they stood pointing and speaking to one another Thorin hailed them: ‘Who are you,’ he called in a very loud voice, ‘that come as if in war to the gates of Thorin son of Thrain, King under the Mountain, and what do you desire?’
And what restores hope? You can see it, too. Encoded in the frequency of uncommon words. And what are the lines at word 86,644?
[16.042] … As they passed through the camp an old man, wrapped in a dark cloak, rose from a tent door where he was sitting and came towards them.
[16.043] ‘Well done! Mr. Baggins!’ he said, clapping Bilbo on the back. ‘There is always more about you than anyone expects!’ It was Gandalf.
The line holds fairly steady throughout the face off, the parleys, the tensions, the goblins and wargs and Dain and the bloodshed right up to the objectively measured, carefully calculated turning point in use of uncommon words.
[17.066] ‘The Eagles!’ cried Bilbo once more, but at that moment a stone hurtling from above smote heavily on his helm, and he fell with a crash and knew no more.