Wow! You outdid yourself. I think this chapter was the best piece of writing you have yet posted, not just in this story but in any story.
The interleaving parts of the letter with the action increased the suspense even while it gave us tantalizing bits of information. And then to see the letter in its entirety at the end -- It confirmed a lot of my speculations, but what a high price for Clark! As if I hadn't felt sorry for him before...
On the positive side, since I was 'incomputercado' (to coin an ugly but descriptive word) for several days and therefore didn't get to read this part until just now, I can read the next part more or less back-to-back with this one.
Brava!
Joy,
Lynn