The reason Harry lied to McGonagall, was because he didn't want her to know his location, and suspected that the only thing she was going to warn him about was that Quirell might be involved in a break in at Azkabam, which he already knows about. If her Patronus had reached earlier Harry, he would have listened to her and told the truth, and she would have arrived, and he certainly wouldn't have time travelled. But then there would have been no attempt to enter Azkabam, and so she wouldn't have know that something was wrong. Since time-turners don't cause these sorts of paradoxes, her Patronus had to find later Harry.
That explains not finding pre-Azkaban Harry. If Harry makes it out of there, there should be a post-Azkaban Harry as well. They want to time it so that they return to Mary's place at about the time they leave. Travel time means there should be three.
- This thread has run its course. You will find newer threads in the discussion section.
Another discussion thread - the fourth - has reached the (arbitrary?) 500 comments threshold, so it's time for a new thread for Eliezer Yudkowsky's widely-praised Harry Potter fanfic.
Most of the paratext and fan-made resources are listed on Mr. LessWrong's author page. There is also AdeleneDawner's collection of most of the previously-published Author's Notes.
Older threads: one, two, three, four. By tag.
Newer threads are in the Discussion section, starting from Part 6.
Spoiler policy as suggested by Unnamed and approved by Eliezer, me, and at least three other upmodders:
It would also be quite sensible and welcome to continue the practice of declaring at the top of your post which chapters you are about to discuss, especially for newly-published ones, so that people who haven't yet seen them can stop reading in time.