IIRC, he jotted down about 10 lines of a projected tale in which Huck
returns as a senile old man, not realizing that he's been gone from St.
Petersburg for decades, and begins asking around for their old friends;
after which sad scene, Tom is located and calms him down, comforting him
...

And that's all. Where did I read that? It's not in anything I have on my
shelf, except possibly the (full) Autobiography?

Thanks for any and all pointers.

/DDD